Incidence of Dengue in India, the effect of climate on dengue transmission and preventive measures of dengue virus infection in India- a systematic review.docx

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Incidence of dengue in India, the effect of climate on dengue transmission
and preventive measures of dengue virus infection in India- a systematic
review.
This thesis is submitted to the University of the West of Scotland in partial fulfilment of the
requirements for the degree of
Master of Public Health (MPH)
Student ID: B00495281
Supervisor Name: Dr Steven Kelly and Dr William McKay Gordie
Submission Date: 15/08/2022
Word count excluding references: 17,629
Similarity score excluding references: 16%

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STATEMENTS
DECLARATION OF OWN WORK
All work presented in this thesis is my own and has been submitted to the University of the
West of Scotland in partial fulfilment of the requirements for the degree of Master of Public
Health. All materials used in this thesis are fully referenced and properly acknowledged.
ETHICAL CONSIDERATION
This thesis is a systematic review based on data from primary studies. Therefore, the thesis
does not require ethical approval because it does not involve animal or human participants.
COPYRIGHT STATEMENT
This thesis has been supplied on the condition that anyone who consults it is understood to
recognise that copyright rests with the author and that no quotation from the thesis and no
information derived from it may be published without the author’s prior written consent.

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TABLE OF CONTENTS
Acknowledgements……………………………………………………………………6
Abstract……………………………………………………………………………….7-8
Table of Abbreviations………………………………………………………………...8-9
Chapter 1: Introduction
1.1.Introduction………………………………………………………………………. 10
1.2.Incidence of dengue infection in India…………………………………………….11-12
1.3.Effect of the Indian climate on dengue transmission………………………………12-13
1.4.Preventive measures against dengue infection…………………………………….13-15
1.5.Research question………………………………………………………………….15
1.6.Aims and objectives………………………………………………………………...15
Chapter 2: Methodology
2.1. Systematic review………………………………………………………………….16
2.2. PICO process……………………………………………………………………….16-17
2.3. Selection criteria……………………………………………………………………17-18
2.4. Search strategy…………………………………………………………………….18
2.5. Search terms……………………………………………………………………….18-19
2.6. Data extraction……………………………………………………………………...19
2.7. Risk of bias…………………………………………………………………………19
2.8. Ethical issues……………………………………………………………………….19
Chapter 3: Results
3.1. Chapter outline……………………………………………………………………20
3.2. Included studies………………………………………………………………….20-21
3.3. Studies selected based on inclusion criteria …………………………………….22-33
3.4. Incidence of dengue infection in India according to serotypes and vectors…….34-35

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3.5. Effect of climatic parameters on dengue transmission within the different states of
India……………………………………………………………………………………35-38
3.6. Preventive strategies used to control dengue infection in India……………………38-44
3.6.1. Surveillance system in India………………………………………………………38-39
3.6.2. Vector control……………………………………………………………………40-41
3.6.3. Community education programs …………………………………………………41-42
3.6.4. Dengue vaccines………………………………………………………………….42-43
3.6.5. GIS mapping………………………………………………………………………43-44
Chapter 4: Discussion:
4.1. Incidence of dengue in India………………………………………………………45-49
4.1.1. Incidence of dengue according to DENV serotypes……………………………45-48
4.1.2. Incidence of dengue in India based on the prevalence of vectors and incidence
rate………………………………………………………………………………………48-49
4.2. Effect of Indian climate on dengue transmission…………………………………49-54
4.2.1. Temperature………………………………………………………………………50-52
4.2.2. Precipitation and humidity……………………………………………………….52-53
4.2.3. Rainfall……………………………………………………………………………53-54
4.3. Preventive interventions……………………………………………………………54-62
4.3.1. Surveillance………………………………………………………………………54-57
4.3.2. Vector control……………………………………………………………………57-59
4.3.3. Community education programs…………………………………………………59-60
4.3.4. Vaccines………………………………………………………………………….60-62
4.3.5. GIS mapping of dengue foci……………………………………………………….62
4.4. Limitations of the study………………………………………………………………63

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Chapter 5: Conclusion and future directions:
5.1. Conclusion…………………………………………………………………………64-65
5.2. Future recommendations……………………………………………………………65-68
5.2.1. Dengue surveillance in India…………………………………………………………65
5.2.2. Vector Control……………………………………………………………………….66
5.2.3. Community programs……………………………………………………………...66
5.2.4. Diagnosis…………………………………………………………………………….66
5.2.5. Treatment……………………………………………………………………………67
5.2.6. GIS mapping……………………………………………………………………….67
5.2.7. Dengue forecast models…………………………………………………………67-68
5.2.8. Research and infrastructure………………………………………………………….68
Chapter 6: References…………………………………………………………………69-79

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ACKNOWLEDGEMENTS
I sincerely thank all the personage involved in this thesis project with me. I want to express
my heartfelt appreciation to the University of the West of Scotland for giving me this
opportunity. I am incredibly grateful to my supervisors Dr William McKay Gordie and Dr
Steven Kelly, for their patience, guidance, and constructive criticism. I am also thankful to
the university librarian Ms Margo Stewart and my classmates from the MPH cohort, who
have provided me with advice and inspiration. Lastly, I did like to acknowledge my parents,
Mr Joel Gerard, and Mrs Delena Joel, for always providing me with emotional support and
helping me with proofreading. Any omission in this acknowledgement doesn’t mean a lack of
gratitude.

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ABSTRACT
Background: Dengue fever is a mosquito-borne arboviral disease that has become a global
public health menace. It is caused by the dengue virus and its four serotypes belonging to the
Flaviviridae family and is spread by Aedes mosquito bites. There has been an emergence of
100,000 dengue cases annually in India. Multiple factors have contributed to the rising of
dengue cases, such as globalisation, urbanisation, ecological, and climatic factors. Studies have
proven that the Indian climate significantly impacts the transmission of dengue vector breeding
and virus transmission. As a result, the Indian public health system has undertaken many
preventive interventions such as surveillance, vector control, community education programs,
vaccines and geospatial analysis.
Objective: More critical information regarding dengue incidence and its association with the
Indian climate and the various preventive strategies in India will help control the infection.
This systematic review will detail the research done by other health professionals and
researchers and identify the literature gaps.
Study design: Systematic review.
Methods: 2 electronic databases and an independent search from a government website were
conducted for quantitative and qualitative studies and statistical data exploring the objectives
of the study.
Results: 38 studies have been selected for the final analysis according to the selection criteria
established. The results showed that the incidence of dengue in India keeps progressively
increasing with a predominance of DENV 2 serotype and Aedes aegypti vector. Climatic
parameters have an indirect relationship with dengue transmission. Various preventive
measures are adopted to control this infection, such as surveillance, vector control, community
education programs, vaccines, and GIS mapping
Conclusion: The incidence of dengue is highest in Uttar Pradesh and lowest in Lakshadweep.
Climatic parameters like elevated temperatures, humidity, precipitation, and rainfall provide
reasonable breeding grounds for the vector. This helps to develop early dengue forecasting
models. Studies have shown that surveillance, vector control, and community programs are the
most common preventive techniques adopted by Indian public health. To prevent future
diseases, many vaccines are undergoing trials in India. Newly adopted interventions like GIS
mapping are also very useful in controlling the infection.

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Keywords: Dengue, India, transmission, incidence, vectors, serotypes, Indian climatic
parameters, vector control, vaccines, surveillance, IDSP, NCVBDC, community programs,
GIS mapping.
TABLE OF ABBREVIATIONS
BCC: Behaviour change communication
CHC: community health centre
DENV: Dengue virus
DHF: Dengue haemorrhagic fever
DNA: Deoxyribonucleic acid
DSS: Dengue shock syndrome
DSU: District Surveillance Unit
EIP: Extrinsic incubation period
ENSO: El Nino Southern Oscillation
GIS: Geographic Information Systems
GPS: Global positioning systems
ICGEB: International Centre for Genetic Engineering and Biotechnology
ICMR: Indian Council of Medical Research
IDSP: Integrated Disease Surveillance Program
L forms: laboratory forms
MAC ELISA: Ig M antibody capture enzyme-linked immunosorbent assay
NCDC: National Centre for Disease Control
NCVBDC: National Centre for Vector-Borne Disease Control
NGO: Non-government organisation
P forms: Presumptive form

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PHC: primary health centre
RNA: Ribonucleic acid
S Forms: Suspected forms
SSU: State surveillance unit
UT: Union Territory
WHO: World Health Organisation

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Chapter 1: INTRODUCTION
1.1.Introduction:
The term dengue originated from the Swahili word Ka-ding pepo, which means cramp-like
seizures (Gupta et al., 2012). A 992 BC Chinese medical encyclopaedia describes dengue
fever as water poison from flying insects (Gupta et al., 2012). Dengue is a neglected tropical
infection that has become one of the most predominant mosquito-borne infections in
developing nations (Roy, Bhattacharjee, 2021). It is endemic in more than 100 nations
(Ganeshkumar et al., 2018) and causes 400 million infection cases and 22,000 deaths globally
each year (Shepard et al., 2016). The dengue infection is an arboviral infection caused by the
dengue virus (DENV) (Chen, Vasilakis, 2011) and is transmitted by the Aedes aegypti and
Aedes albopictus mosquitoes (Devi et al., 2020). This icosahedral-shaped single-stranded
RNA virus belongs to the Flaviviridae genus (Salles et al., 2018) and is transmitted by the
bite of infected female Aedes mosquitoes (Khetarpal, Khanna, 2016). The dengue virus and
its serotypes are transmitted via sylvatic cycles by monkeys and other non-human primates
and human transmission (Chen, Vasilakis, 2011). The dengue virus has four serotypes that
vary according to its antigenicity- DEN 1-4 (Chen, Vasilakis, 2011), and these serotypes have
various subtypes (Roy, Bhattacharjee, 2021). In 2013 in Malaysia, the fifth serotype of
DENV was discovered during genetic analysis when a patient was admitted to a hospital for
fever (Mustafa et al., 2015). All four dengue virus serotypes are found throughout India
except for the newly discovered fifth serotype (Roy, Bhattacharjee, 2021; Mustafa et al.,
2015).
Dengue infection is an acute self-limiting systemic disease (Whitehorn, Simmons, 2011) that
the World Health Organisation (WHO) classified in 1997 into mild asymptomatic dengue
fever, dengue haemorrhagic fever (DHF) and dengue shock syndrome (DSS) (Wang et al.,
2020). Dengue fever is also known as break-bone fever due to intense myalgia and arthralgia
(Gupta et al., 2012). However, in 2009, WHO classified the infection as dengue fever and
dengue with warning signs (Samanta, Sharma, 2015). According to a study, when a particular
serotype infects a person, the immunity is long-lasting against reinfection; however, they
possess only temporary immunity against other serotypes (Wahala, de Silva, 2011). For the
serotypes to function, it depends upon the demographic region it infects and the virus and
host interaction (Gupta, Ballani, 2014).

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1.2.Incidence of dengue infection in India:
In India, the prevalence of the virus and its serotypes has been very complex and evolving
due to its favourable climatic conditions, rapid urbanisation, and extensive travel (Gupta et
al., 2012). Sporadic dengue outbreaks occurred in the past 200 years (Chakravarti et al.,
2012) and were more commonly seen in urban areas (Salje et al., 2019). The first dengue
infection in India was recorded in Chennai in 1780 (Gupta et al., 2012), but the first clinically
proven case was registered in Vellore in 1956 (Chakravarti et al., 2012). A clinically proven
epidemic was witnessed in Calcutta and the eastern coast of India in 1963 (Gupta et al.,
2012), which was the first dengue epidemic that caused 200 deaths (Raheel et al., 2011). In
1956, all four dengue virus serotypes (DEN 1-4) were recorded in various regions of the
nation (Mutheneni et al., 2017). The infection has been transmitted to newer and interior
areas where dengue was non-existent such as Odisha, Arunachal Pradesh, and Mizoram
(Chakravarti et al., 2012). Delhi was the most affected state in the last few years, followed by
Haryana, Punjab, Rajasthan, Uttar Pradesh, Karnataka, Kerala, Tamil Nadu, Maharashtra, and
the Indian Union territories of Andaman and Nicobar Islands and Puducherry (Chakravarti et
al., 2012). A study showed that the number of dengue cases in India peaked in 2013 in
several states in India (Mutheneni et al., 2017). Since then, dengue has become endemic in
almost all the Indian states and is the primary cause of hospitalisation in India (Ganeshkumar
et al., 2018), with approximately 500,000 inpatient admissions (Gupta, Ballani, 2014). In
2016, the National Center for Vector-Borne Diseases Control (NCVBDC) reported more than
100,000 laboratory-confirmed dengue cases (Ganeshkumar et al., 2018). As of 2017, India’s
total number of dengue cases was 12,991,357 (Wilder-Smith, Rupali, 2019). A survey
conducted in 2017 concluded that the current overall prevalence of dengue in India was
48.7% (Murehkar et al., 2019) which was similar to the prevalence in Bangladesh (Salje et
al., 2019) but much lower than the prevalence of dengue in Pakistan (Murhekar et al., 2019).
Recently the NCVBDC reported that every year in India, there are 100,000 infections and
200-400 deaths (NCVBDC, 2021). DENV 2 is one of India’s most prevalent serotypes, and
their coinfections are prevalent all over the country (Alagarasu et al., 2021). Regarding the
type of vectors, Aedes aegypti is more common than Aedes albopictus (Dhiman, Hussein,
2022). In terms of geographical domains, the prevalence of dengue was at its highest in South
India compared to other parts of the country (Wilder-Smith, Rupali, 2019). In terms of
demography, urban regions (70.9%) have a higher prevalence than rural regions (42.3%)

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despite the urbanisation of the rural areas and these numbers are predicted to rise in the
coming years (Wilder-Smith, Rupali, 2019).
The increased incidence of dengue infection has drastically impacted the economy and public
health system (Shepard et al., 2014). It is difficult to do an economic assessment of the
impact caused by dengue due to faulty record-keeping (Raheel et al., 2011). In 2012, the total
medical costs for dengue management in India were $548 million, inpatient admission in the
public sector costs $197.03, and in the private sector hospitals, it costs $230.74 (Shepard et
al., 2014). To prove further, another study mentioned that the total cost of management for
dengue in private sector hospitals was twice the cost of treatment in a government hospital
(Murtola et al., 2010). Therefore, there is a prime need for prevention and control of dengue
infection through surveillance, vector control and community programs (Khetarpal, Khanna,
2016).
1.3 Effect of the Indian climate on dengue transmission:
Several ecological, demographic, and socioeconomic factors play a substantial role in India's
epidemiological triad of dengue infection (Akter et al., 2017). However, the most critical
driver for dengue transmission is the complex Indian climate (Kakarla et al., 2020). This
relationship between climatic factors and dengue transmission varies across geographical
zones and socioeconomic strata (Thammapalo et al., 2008). Climatic parameters such as
temperatures, rainfall index, precipitation and humidity positively influence the breeding of
vectors and the virus replication, which facilitates dengue transmission (Joshua et al., 2020).
A) Temperature: The epidemiological triad of dengue infection is influenced by rising
temperatures (Kakarla et al., 2019). In India, current climate data shows a progressive
yearly temperature increase in Southern states (Kakarla et al., 2020). The elevated
temperatures influence the life cycle of the Aedes mosquitoes, fasten the process of
viral replication (Mutheneni et al., 2017) and shorten the extrinsic incubation period
(interval between mosquito feeding on infected blood and the infectious period)
(Chan, Johansson, 2012). According to a few studies, there is a relationship between a
phenomenon known as El Nino Southern Oscillation (ENSO) and dengue
transmission in tropical countries (Stewart-Ibarra, Lowe, 2013; Pramanik et al., 2020)
by causing a dry hot climate in India favourable for increased vector breeding and
viral replication (Chretien et al., 2015). The practice of water storage in containers
and irrigation techniques in dry climates are also favourable conditions for vector

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breeding (Mills et al., 2010). Furthermore, studies have shown that decreased
temperature causes a reduced number of dengue cases (Mala, Jat, 2019) as the
metabolism of mosquitoes reduces when the temperatures drop (Monintja et al.,
2021).
B) Humidity: Humidity and dengue haemorrhagic fever have a positive relationship with
each other as it influences the survival rate and biting of the mosquitoes and help in
vector breeding and viral replication (Kakarla et al., 2019).
C) Rainfall: The Indian monsoon is a crucial climatic parameter in dengue transmission
(Kakarla et al., 2019) as it provides excellent breeding habitats for the Aedes
mosquitoes due to the abundant stagnant rainwater and the wet grounds
(Guhathakurta et al., 2014). However, heavy rainfall can wipe out the breeding
habitats of the mosquitoes (Jeelani, Sabesan, 2013). Another study suggests that
natural phenomenon like La Nina also causes heavy rainfall in India and promotes
vector breeding (Chretien et al., 2015).
D) Effect of non-climatic factors on climatic factors: Non-climatic factors have an
indirect relationship with meteorological factors like temperature, rainfall, and
humidity (Campbell-Lendrum et al., 2015). Demographic and ecological factors like
water storage practices in containers, urbanisation, irrigation and farming practices,
and extensive international travel cause increased vector reproduction and faster virus
transmission (WHO, 2014).
The existing literature proves a link between climate and dengue transmission (Colon-
Gonzalez et al., 2013). It has become easier to forecast dengue based on meteorological
parameters (Colon-Gonzalez et al., 2013).
1.4. Preventive measures against dengue infection:
Several preventive strategies are adopted to control the dengue infection in India (Rather et
al., 2017).
A) Surveillance: There are three types of surveillance undertaken in India: active, passive
and sentinel surveillance (Rather et al., 2017). Active surveillance is undertaken by
national government programs such as NCVBDC and Integrated Disease Surveillance
Program (IDSP) (Modi et al., 2018). Passive surveillance is conducted by hospitals,
primary care centres and broad networks (Rather et al., 2017). Sentinel surveillance is
the third type of surveillance by collecting data from selected health centres with

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sufficient resources, and this is also done by NCVBDC and IDSP (Rather et al.,
2017). All the three types of surveillance are integrated together to track and monitor
the dengue cases (Pilot et al., 2020).
B) Vector control measures: Vector control is one of India's most adopted preventive
interventions (Gupta et al.., 2012). Environmental prevention strategies include
eliminating vector breeding sites such as unused water storage containers or improper
waste management (Harapan et al., 2020). Antilarval chemicals such as Malathion,
Temephos and Fenthion are very effective in controlling the mosquito population
density (Tikar et al., 2008). Recently plant-based compounds such as Flavonoid
compounds (Kumar et al., 2010), benzene, chloroform and methanol extracts are
commonly used to control vector population as they are biodegradable (Govindarajan,
Karuppanan, 2011). A study found that indoor residual spraying and indoor space
spraying reduce the population of adult mosquitoes (Samuel et al., 2017). Several
behavioural protective interventions are adopted to stop from getting exposed to
mosquitoes, such as mosquito bed nets and window screens (Alvarado-Castro et al.,
2017). However, these interventions depend on community compliance and
knowledge regarding disease transmission and control (Alvarado-Castro et al., 2017).
C) Community education programs: Programs via pamphlets, demonstrations, and audio-
visual aids about preventive strategies against dengue infection (George et al., 2017)
are aimed to enhance knowledge among communities at grass root levels in India
(Gupta et al., 2012). Studies have suggested that these community programs have
changed the course of dengue transmission by reducing the number of cases
throughout the countries (Abbas et al., 2013). Despite having adequate knowledge
regarding dengue, specific communities lack a precautionary attitude towards
controlling the infection (Mathur et al., 2020).
D) Vaccines: Since the 1940s, dengue vaccines have been in developmental stages (Guy
et al., 2011). The Indian Council of Medical Research (ICMR) and the US National
Institute of Health (NIH) have been developing dengue vaccines since 1987 (Fauci et
al., 2019). Two vaccines have been undergoing trials in India: TetraVax-DV and
DSV4 (Ramasamy et al., 2018). Dengvaxia, developed by Sanofi in 2015, has not yet
been approved as the Indian government has some concerns regarding its safety
(Swaminathan, Khanna, 2019).
E) GIS mapping of dengue focus: GIS stands for geographic information system, an
advanced physical control measure used for plotting epidemiological maps

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(Zambrano et al., 2017). It is used to analyse and locate the dengue infection foci
(Rather et al., 2017) to help contain the dengue infection in a particular area (Gandhi
et al., 2017) and decrease morbidity and mortality (Singh, Chaturvedi, 2021).
1.5. Research question:
How do the Indian climatic factors and the different preventive measures adopted by the
Indian public health systems affect the incidence of dengue infection?
1.6. Aims and Objectives:
This systematic review is conducted with the above background to:
- Explore the incidence of dengue infection in India: incidence rates, serotypes, vectors.
- Analyse the association between Indian climate and dengue transmission
- Understand the different preventive strategies used to control dengue infection in
India.

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Chapter 2: METHODOLOGY
2.1. Systematic review:
A systematic review or overview is a collection of literature searched, gathered, and critically
collated into a comprehensive study to answer the specific research question (Ahn, Kang,
2018). The reviews must be transparent, should be focused on the formulated research question
and must be systematically organised for clear understanding (Muka et al., 2019). The
statistical data obtained from multiple primary research articles are analysed to conclude the
specific issue being researched, and this, in turn, will reduce bias and errors (Gopalakrisnan,
Ganeshkumar, 2013). Therefore, to obtain a favourable research outcome, the review is
conducted by following specific steps (Ahn, Kang, 2018). The first step is selecting a logical
research topic and formulating an appropriate research question by defining the PICO
parameters vital to the research (Stewart et al., 2015). The next step was determining the proper
inclusion and exclusion criteria and developing the search strategy to help the researcher
identify the essential journal articles (Uman, 2011). With the help of PRISMA guidelines,
different studies were selected that fulfilled the inclusion criteria. A flowchart was created to
indicate the number of studies selected and a table to list the chosen literature with the authors’
names and conclusions (Page et al., 2021). Upon completing this table, the statistical data from
these papers were qualitatively analysed, interpreted, and consolidated into a comprehensive
literature review (Uman, 2011).
2.2. PICO process:
PICO stands for Population, Intervention, Comparison and Outcome (Schiavenato, Chu, 2021).
The PICO process was utilised in evidence-based practice to generate a well-structured
research question and is commonly intended for research conducted in healthcare settings
(Schiavenato, Chu, 2021). PICO facilitates an easy search strategy and reduces the confusion
in the selection of appropriate search terms for searching research articles in different databases
(Ford, Melnyk, 2019). Therefore, the research question and search words effectively search
and generate unbiased evidence that answers the research question (Ford, Melnyk, 2019).

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Table 2.1. PICO Table
Population
(36)
Andaman and Nicobar Islands, Andhra Pradesh, Arunachal Pradesh,
Assam, Bihar, Chandigarh, Chattisgarh, Daman & Diu, Delhi, Goa, Gujarat,
Haryana, Himachal Pradesh, Jammu & Kashmir, Jharkhand, Karnataka,
Kerala, Ladakh, Lakshadweep, Madhya Pradesh, Maharashtra, Manipur,
Meghalaya, Mizoram, Nagaland, Odisha, Puducherry, Punjab, Rajasthan,
Sikkim, Tamil Nadu, Tripura, Telangana, Uttar Pradesh, Uttarakhand, West
Bengal
Interventions
(5)
Surveillance AND vector control AND community education program
AND vaccination for dengue AND GIS mapping
Comparison
(2)
Incidence of dengue and climatic factors across different states of India
Outcome (2) Incidence of dengue AND effect of Climatic factors on dengue
2.3. Selection Criteria:
Table 2.2. Selection criteria
Inclusion Criteria Exclusion Criteria
Population from all the age groups and
genders from all the 28 states and 8 union
territories of India included.
Articles irrelevant to the research question:
dengue transmission in other countries,
entomological and genetic studies are
excluded.
Only completed articles in English are
included.
Articles published in other languages are
exempt.
Only research articles published from 1st
January 2010 to 30th
June 2022 are included
for data analysis as older articles will have
significant differences in the conclusions.
Articles published before January 1st
2010,
are not considered for the data analysis in the
systematic review.
Systematic reviews, randomised control
trials and meta-analyses with appropriate
abstracts, results and discussions are
included in the study.
Articles without a significant introduction or
abstract, results and discussions are not
included.

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Only free full-text articles and reviews are
included in the study
Paid articles and reviews are not included in
the study.
2.4. Search Strategy:
For this systematic review, articles were searched according to PRISMA guidelines and the
formulated research question via two databases- PubMed and Web of Science with the help of
the online library of the University of the West of Scotland. An independent search was
conducted from the government NCVBDC website to acquire statistical information on dengue
incidence. Necessary Boolean terms and operators were utilised to avoid excluding relevant
articles. A comprehensive search was conducted from publications dating from 1st
January
2010 to 30th
June 2022. Inclusion and exclusion criteria were recognised, and Boolean terms
were used to identify the articles in English for final analysis. Duplicate reports were removed
manually, and articles describing dengue in India were considered. The identified articles were
screened thoroughly and then tested for eligibility. Articles irrelevant to the research question,
studies without abstracts, unsatisfactory results, conclusions, lack of free full texts, and texts in
foreign languages were excluded. Articles describing dengue infection in other countries,
entomological and genetic studies were excluded. The eligible studies described the dengue
virus's microbiology, clinical picture, dengue incidence in India, dengue transmission
association with Indian climatic factors, and preventive strategies. The complete search
strategy and included studies for data analysis are described in the results section
2.5. Search terms:
Specific keywords based on the PICO framework were searched: Dengue, India, epidemiology,
transmission, incidence, vectors, serotypes, Indian climatic parameters, surveillance,
NCVBDC, IDSP, vector control, community education programs, vaccines, GIS mapping.
In addition, many Boolean terms were utilised, such as “dengue and/or epidemiology in India”,
“dengue and/or incidence in India”, “dengue and/or serotypes in India”, “dengue and/or
economic and social impact in India”, “dengue and/or south India”, “dengue and/or north
India”, “dengue and/or west India”, “dengue and/or east India”, “dengue and/or northeast
India”, “dengue and/or climatic factors in India”, “dengue and/or temperature in India”,
“dengue and/or monsoon in India”, “dengue and/or vectors in India”, “dengue and/or

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preventive measures in India”, “dengue and/or vaccines in India”, “dengue and/or surveillance
in India”, “dengue and/or IDSP”, “dengue and/or NCVBDC”, “dengue and/or health education
in India”, “dengue and/or biological or chemical vector control in India”, “dengue and/or GIS
mapping”.
2.6. Data extraction:
This is a process where relevant information and results are obtained based on the journal
studies selected based on the selection criteria and the research question. Assessment of the
quality of the study is made after the articles are identified for final analysis. The articles are
selected eligible based on the country where the dengue transmission occurs, Indian climatic
conditions, preventive strategies, population, study designs and results.
2.7. Risk of bias:
Factors that cause errors are inaccurate study design, poor results, formulating an incomplete
research question, and emotional bias toward cultural practices that lead to unreliable outcomes
in the systematic study (Wolff et al., 2019). These errors are known as a bias which must be
reduced to provide accurate results in the systematic review (Wolff et al., 2019). Assessment
of the risk of bias is essential for a systematic review as it provides consistency, quality, and
reliability (Navarro et al., 2021).
2.8. Ethical issues:
This independent study does not involve any primary data collection and surveys conducted.
The journal articles selected were thoroughly searched to produce favourable outcomes.
Feedback provided by the supervisor has been considered to reduce the bias in the study.

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Chapter 3: Results
3.1. Chapter Outline:
This chapter will define PRISMA, explain the search strategy in detail, draw the PRISMA
flowchart, describe the included studies in a tabulated manner, and explain in detail the
selected studies under subheadings based on the aims and objectives.
3.2. Included studies:
PRISMA statement stands for Preferred Reporting Items for Systematic reviews and Meta-
analyses and was introduced in 2009 (Moher et al., 2010). It was developed to help researchers
conduct transparent, systematic reviews, explain the rationale behind the research and analyse
and interpret the data found in published research articles using a 27-item checklist and a
flowchart (Moher et al., 2010). Recently in 2020, the guidelines were updated because there
have been changes in the methodology of systematic reviews (Page et al., 2021). PRISMA
2020 statement gives new and improved guidelines on identifying, appraising, and interpreting
the studies (Page et al., 2021).
The search yielded six hundred eighty-three articles in PubMed and three hundred articles on
the Web of Science related to dengue after using the search terms dengue, incidence, climate,
preventive interventions, and India. Statistical data related to the incidence of dengue infection
was obtained from the NCVBDC official website after an independent search. Two hundred
thirty-seven were identified as duplicate articles. The remaining seven hundred and forty-six
articles were initially screened using the selection criteria, and three hundred fifty articles were
selected based on the relevant title and abstract. Three hundred ninety-six articles were
excluded as they were irrelevant to the systematic review. This is due to the lack of abstracts,
use of foreign language, and describing dengue infection in other countries. The search was
refined using the selection criteria and keywords such as Indian climatic conditions, preventive
measures in India, surveillance, vaccines, and vector control. After a thorough screening, one
hundred twenty-four articles were found eligible for review. Two hundred twenty-six articles
were excluded after screening because of irrelevancy to the research question, studies
describing entomological and genetic studies, exploring treatment and diagnostics. After
further eligibility testing and excluding eighty-seven articles due to lack of free full texts, thirty-
eight articles were found to fulfil all the inclusion and exclusion criteria established.

21
Flowchart 3.1: PRISMA FLOWCHART
Total Articles identified via PubMed (n=683) and Web of Science (n=
300). Total (n= 983)
Independent search (1)- NCVBDC website
Duplicate articles removed
(n=237)
Articles initially screened
(n=746)
Articles excluded after initial
screening (n=396)
Screening
Articles after initial screening
and further screened for
eligibility(n=350)
Articles excluded after further
screening (n=226)
Eligibility
Including
Articles after eligibility testing
(n= 124)
Articles included for study
(n= 37 + 1 from independent
search = 38)
Articles excluded after further
eligibility testing (n= 87)
Identification

22
3.3. Studies selected based on the inclusion criteria: (Table 3.1)
Title Author and
publication year
Journal Methodology and
Conclusion
1. Dengue in India Gupta, N.,
Srivastava, S., Jain,
A., Chaturvedi, U.C.
(2012)
Indian Journal of Medical
Research, 136(3), pp.373-390.
PMID: 23041731.
A qualitative study
that describes
dengue
epidemiology and
preventive strategies
against dengue
transmission.
2. Dengue
infection in
India- a
systematic
review and
meta-analysis
Ganeshkumar, P.,
Murhekar, M.V.,
Poornima, V.,
Saravanakumar, V.,
Sukumaran, K.,
Anadaselvasankar,
A., John, D.,
Mehendale, S.M.
(2018)
PLOS Neglected Tropical
Diseases, 12(7): e0006618. Doi:
10.1371/journal.pntd.0006618.
A quantitative study
that describes the
increased dengue
seroprevalence in the
country.
3. Dengue situation
in India:
Suitability and
transmission
potential model
for present and
projected
climate change
scenarios
Kakarla, S.G.,
Bhimala, K.R.,
Kadiri, M.R.,
Kumaraswamy, S.,
Mutheneni, S.R.
(2020).
Science of the total
environment, 739, 140336. Doi:
10.1016/j.scitotenv.2020.14033
6. (Accessed on 07/06/2022).
that highlights the
different climatic
parameters and their
association with EIP
and viral replication.
4. Dengue burden
in India: recent
trends and
importance of
Mutheneni, S.R.,
Morse, A.P.,
Caminade, C.,
Upadhyayula, S.M.
(2017).
Emerging microbes and
infections, 6(8): e70. Doi:
10.1038/emi.2017.57.
that describes how
dengue transmission
affects the Indian
climatic parameters.

23
climatic
parameters
5. Dengue virus:
epidemiology,
biology, and
disease
aetiology.
Roy, S.K.,
Bhattacharjee, S.
(2021).
Canadian Journal of
Microbiology, 67(10). Doi:
10.1139/cjm-2020-0572.
(Accessed on 04/07/2022).
A qualitative study
that highlights the
different serotypes
that cause the
infection and the
disease severity and
how it helps to
predict the
epidemiology.
6. Serotype and
genotype
diversity of
dengue viruses
circulating in
India: a multi-
centre
retrospective
study involving
the Virus
Research
Diagnostic
Laboratory
Network in
2018.
Alagarasu, K., Patil,
J.A., Kakade, M.B.,
More, A.M.,
Yogesh, B., Newase,
P., Jadhav, S.M.,
Parashar, D., Kaur,
H., Gupta, N., Vijay,
N., Narayan, J.,
Shah, P.S., VRDL
Team (2021)
International journal of
infectious diseases: IJID, 111,
pp.242-252. Doi:
10.1016.j.ijid.2021.08.045.
that highlights the
prevalence of
circulating dengue
serotypes and the
regional differences.
7. Dengue virus
serotypes and
genotypic
characterisation
from northeast
India.
Chetry, S., Khan,
S.A., Dutta, P.,
Apum, B., Medhi,
P.S., Saikia, D.C.,
Temsu, T., Mawii,
L., Marak, B.C.
(2019).
Journal of Medical Virology,
91(6), pp.918-927. Doi:
10.1002/jmv.25418.
that describes the
prevalence of
circulating serotypes
in North-eastern
regions.

24
8. A retrospective
study of climate
change affecting
dengue:
evidences,
challenges and
future directions.
Bhatia, S., Bansal,
D., Patil, S., Pandya,
S., Ilyas, Q.M.,
Imran, S. (2022).
Frontiers in Public Health, 10:
884645. Doi:
10.3389/fpubh.2022.884645.
A qualitative study
that suggests that
tracking the climatic
parameters will help
to establish the
dengue surveillance
system in the
country.
9. Distribution
expansion of
dengue vectors
and climate
change in India.
Hussain, S.S.A.,
Dhiman, R.C.
(2022).
Advancing Earth and Space
Science, 6(6): e2021GH000477.
Doi: 10.1029/2021GH000477.
that concluded that
maps generated
based on climatic
factors and dengue
vectors might be
helpful in dengue
surveillance in India.
10. Burden of
dengue with
related
entomological
and climatic
characteristics in
Surat city,
Gujarat, India,
2011-2016: an
analysis of
surveillance
data.
Bajwala, V.R., John,
D., Rajasekar, D.,
Eapen, A.,
Murhekar, M.V.
(2020).
The American Journal of
Tropical Medicine and Hygiene,
103(1), pp.142-148. Doi:
10.4269/ajtmh.19-0967.
that concludes that
dengue transmission
increases post-
monsoon, and
humidity and rainfall
favour faster vector
reproduction.

25
11. Modeling and
prediction of
dengue
occurrences in
Kolkata, India,
based on climate
factors.
Bal, S., Sodoudi, S.
(2020).
International Journal of
Biometeorology, 164, pp.1379-
1391. Doi:
https://doi.org/10.1007/s00484-
020-01918-9
that describes the
relationship between
dengue transmission
and climatic factors
in Kolkata, West
Bengal.
12. El Nino
Southern
Oscillation as an
early warning
tool for dengue
outbreak in
India.
Pramanik, M.,
Singh, P., Kumar,
G., Ojha, V.P.,
Dhiman, R.C. (2020)
BMC Public Health, 20: 1498.
Doi: 10.1186/s12889-020-
09609-1
that describes the
positive correlation
between rainfall
index and dengue
case index
13. Lag effect of
climatic
variables on
dengue burden
in India
Kakarla, S.G.,
Caminade, C.,
Mutheneni, S.R.,
Morse, A.P.,
Upadhyayula, S.M.,
Kadiri, M.R.,
Kumaraswamy, S.
(2019)
Epidemiology and infection,
147: e170. Doi:
10.1017/S0950268819000608.
that tells that there is
a non-linear
association between
climatic factors and
dengue transmission.
14. Development
and use of a
reproducible
framework for
spatiotemporal
climatic risk
assessment and
its association
Singh, G., Mitra, A.,
Soman, B. (2022).
Indian Journal of Community
Medicine, 47(1), pp.50-54. Doi:
10.4103/ijcm.ijcm_862_21.
that suggests that the
infectious disease
model can be used to
comprehend the
disease
epidemiology and

26
with decadal
trend of dengue
in India.
establish a robust
surveillance system
15. Implications of
meteorological
and
physiographical
parameters on
dengue
occurrences in
Delhi.
Mala, S., Jat,
M.K. (2019).
(Accessed on
05/07/2022).
Science of The Total
Environment, 650(2), pp.2267-
2283. Doi:
10.1016/j.scitotenv.2018.09.357
.
that concludes that
dengue transmission
in Delhi is more in
the post-monsoon
season.
16. Forecasting
dengue hotspots
associated with
variation in
meteorological
parameters using
regression and
time series
model.
Patil, S., Pandya, S.
(2021).
Frontiers in Public Health, 9:
798034. Doi:
10.3389/fpubh.2021.798034.
describes how
monsoon and humid
climates positively
correlate with
dengue transmission.
17. Episodes of the
epidemiological
factors
correlated with
prevailing viral
infections with
dengue virus and
molecular
characterisation
of serotype-
specific dengue
virus circulation
in eastern India.
Rao, M.R.K.,
Padhy, R.N.,
Das, M.K.
(2018).
Infection, genetics and
evolution, 58, pp.40-49. Doi:
10.1016/j.meegid.2017.12.005.
that describes the
circulation of
different serotypes
of the coinfections in
Eastern India
requires a stable
surveillance system.

27
18. Joint effects of
climate
variability and
socioecological
factors on
dengue
transmission-
epidemiological
evidence.
Akter, R., Hu, W.,
Naish, S., Banu, S.,
Tong, S. (2017).
Tropical Medicine and
International Health, 22(6),
pp.656-669. Doi:
10.1111/tmi.12868.
A qualitative study
that highlights gaps
in the literature
regarding the
association between
climate and socio-
ecological factors.
19. Current
perspectives on
the spread of
dengue in India.
Gupta, E., Ballani,
N. (2014).
Infection and Drug Resistance,
7, pp.337-342. Doi:
10.2147/IDR S55376.
A qualitative study
that describes the
epidemiology,
microbiology and
preventive
interventions and
how research has
helped control
dengue infection.
20. Fight against
dengue in India:
progresses and
challenges.
Gupta, B., Reddy,
B.P.N. (2013).
Parasitology Research, 112,
pp.1367-1378. Doi:
10.1007/s00436-013-3342-2
A qualitative study
that described an
extensive need for
research, public
participation and
reliable public health
measures.
21. Understanding
India’s urban
dengue
surveillance: a
Pilot, E., Nittas, V.,
Murthy, G.V.S.
(2020).
Global Public Health, 15(11),
pp. 1702-1717. Doi:
10.1080/17441692.2020.176767
4.
A qualitative study
that describes the
need for increased

28
qualitative
policy analysis
of Hyderabad
district.
investment in public
health and a need for
an intelligent system
of surveillance.
22. The
organisation,
implementation
and functioning
of dengue
surveillance in
India- a
systematic
scoping review.
Nittas, V., Pilot, E.,
Murthy, G.V.S.
(2019).
Research for Public Health,
16(4): 661. Doi:
10.3390/ijerph16040661.
A qualitative study
that describes the
functions, strengths,
and limitations of the
surveillance systems
in India.
23. Outbreak of
dengue in Tamil
Nadu, India.
Chandran, R.,
Azeez, P.A. (2015)
Current Science, 109(1),
pp.171-176. Available at:
https://www.jstor.org/stable/249
05701
A qualitative study
that concentrates on
the outbreak of
dengue infection in
Tamil Nadu and its
association with
environmental
factors and
preventive
interventions
adopted to curb it.
24. Profile of
communicable
diseases reported
under integrated
disease
surveillance
Ramdas, I., Nair, S.
(2020).
Journal of family medicine and
primary care, 9(8), pp.4165-
4169. Doi:
10.4103/jfmpc.jfmpc_552_20.
A qualitative study
that describes how
the incidence of
infectious diseases
like dengue that have

29
programme from
a teaching
hospital.
been diagnosed and
reported would help
track and monitor
the transmission.
25. Assessment of
the core and
support
functions of the
Integrated
Disease
Surveillance
system in
Maharashtra,
India.
Phalkey, R.K.,
Shukla, S., Shardul,
S., Ashtekar, N.,
Valsa, S., Awate, P.,
Marx, M. (2013).
BMC Public Health, 13: 575.
Doi: 10.1186/1471-2458-13-
575.
A qualitative study
that describes there
had been a
significant
improvement in
transmitting
transmissible
infections after
adequately
implementing the
surveillance
programs.
26. Towards
Integrated
Management of
Dengue in
Mumbai.
Paradkar, P.N.,
Sahasrabudhe, P.R.,
Sawant, M.G.,
Mukherjee, S.,
Blasdell, K.R.
(2021)
Viruses, 13(12): 2436. Doi:
10.3390/v13122436. The qualitative study
concluded that
integrating a sound
surveillance system
and mosquito control
strategies has helped
control dengue
transmission.
27. Plant extracts as
1potential
mosquito
larvicides.
Ghosh, A.,
Chowdhury, N.,
Chandra, G. (2012).
Indian Journal of Medical
Research, 135(5), pp.581-598.
PMID: 22771587.
A qualitative study
concluded that plant-
based compounds

30
are more effective
vector control
measures than
chemical-based
compounds.
28. Mosquito
larvicidal and
ovicidal
properties of
Eclipta alba (L.)
Hassk
(Asteraceae)
against
chikungunya
vector, Aedes
aegypti (Linn.)
(Diptera:
Culicidae).
Govindarajan, M.,
Karuppanan, P.
(2011).
Asian Pacific Journal of
Tropical Medicine, 4(1), pp.24-
28. Doi: 10.1016/S1995-
7645(11)60026-6. (Accessed on
10/06/2022).
that describes E.alba
extracts is a good
vector control
measure.
29. Dengue fever:
Causes,
complications,
and vaccine
strategies.
Khetarpal, N.,
Khanna, I. (2016).
Journal of Immunology
Research, 2016: 6803098. Doi:
10.1155/2016/6803098.
The qualitative study
concluded that there
is a need for
extensive research
and quick
implementation of
vaccines for dengue
viral fever.
30. Dengue vaccine
development:
Swaminathan, S.,
Khanna, N. (2019).
International Society for
Infectious Diseases, 84, pp.S80-
A qualitative study
that describes

31
Global and
Indian scenarios
S86. Doi:
10.1016/j.ijid.2019.01.029.
different vaccines
under trial in India.
31. A tetravalent
virus-like
particle vaccine
designed to
display domain
III of dengue
envelope
proteins induces
multiserotype
neutralising
antibodies in
mice and
macaques, which
confer protection
against
antibody-
dependent
enhancement in
AG129 mice.
Ramasamy, V.,
Arora, V., Shukla,
R., Poddar, A.,
Shanmugam, R.K.,
White, L.J..,
Mattocks, M.M.,
Raut, R., Perween,
A., Tyagi, P., de
Silva, A.M.,
Bhaumik, S.K.,
Kaja, M.R.,
Villinger, F.,
Ahmed, R.,
Johnston, R.E.,
Swaminathan, S.,
Khanna, N. (2018).
PLOS Neglected Tropical
Diseases, 12(1): e0006191. Doi:
10.1371/journal.pntd.0006191.
The quantitative
study concluded that
indigenous vaccines
were being produced
in India and
undergoing trials.
32. Community
engagement to
control dengue
and another
vector-borne
disease in
Alappuzha
municipality,
Kerala, India.
Gopalan, R.B.,
Babu, B.V.,
Sugunan, A.P.,
Murali, A., Ma,
M.S.,
Balasubramanian,
R., Philip, S. (2021).
Pathogens and Global Health,
115(4), p.258-266. Doi:
10.1080/20477724.2021.189088
6.
The quantitative
study concluded that
community
programs in the form
of educative sessions
benefited dengue
control in a village
in Kerala.

32
33. Impact of health
education-based
intervention on
community’s
awareness of
dengue and its
prevention in
Delhi, India
Yadlapalli, S.K.,
Burman, D., Kumari,
R., Lamkang, A.S.,
Babu, B.V. (2017).
Global Health Promotion, 26(1),
pp.50-59. Doi:
10.1177/1757975916686912.
concluded that
community
programs have
reduced dengue
transmission in
Delhi, India.
34. Community-
based
interventional
study on dengue
awareness and
vector control in
a rural
population in
Ernakulam,
Kerala.
George, L.S., S., A.,
Paul, N., Leelamoni,
K. (2017).
International journal of
community medicine and public
health, 4(4), pp.962-967. Doi:
10.18203/2394-
6040.ijcmph20170984.
highlights that
community
education reduces
dengue virus
transmission.
35. Revitalising
community
engagement and
surveillance
challenges for
strengthening
dengue control
in Jodhpur,
Western
Rajasthan, India-
a mixed method
study.
Mathur, D., Patel,
M., Vyas, P.,
Kaushal, R., Dash,
G.C., Goel, A.D.,
Bhardwaj, P., Gupta,
M.K., Joshi, N.K.
(2020).
Journal of infection and public
health, 13(11), pp.1755-1761.
Doi: 10.1016/j.jiph.2020.08.005.
(Accessed on 06/07/2022).
The mixed study
concluded that
community
programs had
enriched the
people’s knowledge
about dengue and its
preventive measures
in Western
Rajasthan.
36. Temporal
variation and
geospatial
Singh, P.S.,
Chaturvedi, H.K.
(2021).
BMJ Open, 11(2): e043848.
Doi: 10.1136/bmjopen-2020-
043848.
The mixed study
concluded that GIS
technology has

33
clustering of
dengue in Delhi,
India 2015-2018.
helped to monitor
dengue transmission
in Delhi and has
reduced the
infection.
37. Data mapping of
vector-borne
disease with
geographical
information
system and
global position
system
technology: in
tribal areas
Khammam
district,
Telangana State.
Gandhi, G., Chapla,
J., Naik, B.R.
(2017).
Mosquito Research, 4(2), pp.39-
43. Available at:
http://www.dipterajournal.com/
pdf/2017/vol4issue2/PartA/3-6-
10-404.pdf (Accessed on
10/06/2022).
concluded that GIS
technology has
helped to track and
monitor the dengue
disease through
spatial parameters.
38. Dengue/DHF
situation in
India.
National Center for
Vector-Borne
disease control
(NCVBDC) (2021)
Available at:
https://nvbdcp.gov.in/index4.ph
p?lang=1&level=0&linkid=431
&lid=3715
Government
database reporting
the incidence of
dengue infection in
all the states and
union territories in
India.

34
3.4. Incidence of dengue infection in India according to the serotypes, vectors and
incidence rate:
Literature characteristics:
India is a country comprised of 28 states and 8 Union territories. Out of the thirty-eight articles
selected, the data was gathered from ten articles from January 1st,
2010, to June 30th
2022, after
a database search. Seven articles focus on the history of dengue in India and the seroprevalence
of dengue in the different regions of India since the 1980s (Gupta et al.,2012; Ganeshkumar et
al., 2018; Kakarla et al., 2020; Mutheneni et al., 2017; Roy, Bhattacharjee, 2021; Alagarasu et
al., 2021; Chetry et al., 2019). Two articles focus on the prevalence of mosquito vectors in
India (Bhatia et al., 2022; Hussein, Dhiman, 2022). The statistical data for the dengue incidence
rate for 28 states and 8 Union territories are taken from the official website of the National
Center for Vector-Borne disease control (NCVBDC) after an independent search to compare
the incidence rate and dengue transmission across the country.
The outcomes of the selected articles show that the incidence of dengue in India has increased
over the last fifty years, DENV 2 serotype is the most prevalent serotype, and Aedes aegypti is
the most prevalent vector in India (Gupta et al., 2012; Roy, Bhattacharjee, 2021; Hussein,
Dhiman, 2022). Regionally, Uttar Pradesh had the highest incidence whereas Lakshadweep
had the lowest incidence in 2021 (NCVBDC, 2021). The key findings from the selected studies
are summarised in table 3.2.
Table 3.2: Incidence of dengue in India based on history, serotypes, and vectors, (Roy,
Bhattacharjee, 2021; Alagarasu et al., 2021; Chetry et al., 2019; Hussein, Dhiman, 2022)
First outbreak of dengue in India Chennai, Tamil Nadu -1780
First laboratory confirmed epidemic in India Kolkata, West Bengal- 1963
Second major epidemic in India Delhi and Lucknow- 1996
First DENV 1 infection Vellore, Tamil Nadu- 1956
Current DENV 1 infection Northeastern and southwestern states.
Current DENV 2 infection Northwestern, Central India, and the eastern
coast.
Current DENV 3 infection Haryana and Madhya Pradesh

35
First DENV 4 infection Kanpur, Uttar Pradesh- the 1960s (specific
year not determined)
Current DENV 4 infections Andaman and Nicobar Islands
First coinfection by dengue serotypes Vellore, Tamil Nadu by DENV 1,2,3 &4-
1968.
Current coinfections by dengue serotypes Eastern and western coasts
Aedes aegypti mosquitoes (Vectors) Most of the Northern states and the south
peninsula
Aedes albopictus mosquitoes (Vectors) West coast of India
3.5. Effect of climatic parameters on the dengue transmission within the different states/
union territories (UT) of India:
Climate change has affected dengue transmission in India. Out of the selected thirty-eight
articles, the data was gathered from twelve articles from January 1st
2010, to June 30th
June
2022. One article predominantly focuses on the association of dengue transmission with the El
Nino and La Nina phenomena and its overall impact on the country (Pramanik et al., 2020).
Eleven articles concentrate on the different climatic conditions in India and their effect on
vectors and virus replication and focus on the regional dengue transmission across different
climatic zones – Kolkata (West Bengal), Kerala, Gujarat, Delhi, Rajasthan, Punjab, and
Haryana (Bajwala et al., 2020; Bal, Sodoudi, 2020; Mutheneni et al., 2017; Kakarla et al., 2019;
Kakarla et al., 2020; Singh et al., 2022; Bhatia et al., 2022; Mala, Jat, 2019; Rao et al., 2018;
Patil, Pandya, 2021; Akter et al., 2017).
The key findings of the selected articles indicate that elevated temperatures, humidity, excess
rainfall during monsoon and natural phenomena like El Nino and La Nina have positively
correlated with dengue transmission (Mutheneni et al., 2017; Kakarla et al., 2019; Kakarla et
al., 2020; Pramanik et al., 2020). However, there is a negative correlation between winter and
dengue transmission (Mala, Jat, 2019). The majority of the dengue cases are observed during
monsoon season with a peak rise in August and September (Mutheneni et al., 2017; Kakarla et
al., 2020). The reports also indicate gaps in the literature regarding climate association and
dengue transmission and the need for research in this area (Mutheneni et al., 2017; Kakarla et

36
al., 2019; Kakarla et al., 2020). The key findings from the selected studies are summarised in
tables 3.3 and 3.4.
Table 3.3: Association between the incidence rate of dengue and Indian climatic factors
(NCVBDC, 2021; Mutheneni et al., 2017; Kakarla et al., 2019; Kakarla et al., 2020):
No. Region State/Union
territory
Incidence (as of
NCVBDC, 2021)
Climatic association
with dengue
transmission (Incidence
more)
1. North Arunachal
Pradesh
7 Monsoon and post-
monsoon
2. North Bihar 633 Monsoon and post-
monsoon
3. North Chattisgarh 1086 Monsoon and post-
monsoon
4. North Haryana 11835 Monsoon and post-
monsoon
5. North Jharkhand 220 Summer, monsoon and
post-monsoon
6. North Madhya Pradesh 15592 Post-monsoon
7. North Punjab 23389 Monsoon and post-
monsoon
8. North Sikkim 243 Monsoon
9. North Uttar Pradesh 29750 (highest) Summer
10. North Uttarakhand 738 Monsoon
11. Northeast Assam 103 Summer
12. Northeast Manipur 203 Summer and monsoon
13. Northeast Meghalaya 129 Summer and monsoon
14. Northeast Mizoram 83 Summer and monsoon
15. Northeast Nagaland 24 Summer, monsoon and
post-monsoon
16. West Goa 649 Monsoon

37
17. West Gujarat 10983 Monsoon and post-
monsoon
18. West Maharashtra 12720 Monsoon and post-
monsoon
19. West Rajasthan 20749 Monsoon and post-
monsoon
20. East Himachal Pradesh 349 Summer and monsoon
21. East Odisha 7548 Summer, monsoon and
post-monsoon
22. East Tripura 349 Monsoon and post-
monsoon
23. East West Bengal 8264 Monsoon and post-
monsoon
24. South Andhra Pradesh 4760 Summer, monsoon and
post-monsoon
25. South Karnataka 7393 Post-monsoon
26. South Kerala 3251 Monsoon and post-
monsoon
27. South Tamil Nadu 6039 Post-monsoon
28. South Telangana 7135 Monsoon and post-
monsoon
29. UT Andaman &
Nicobar Islands
175 Monsoon and post-
monsoon
30. UT Chandigarh 1596 Monsoon and post-
monsoon
31. UT D & N Haveli 547 Monsoon
32. UT Daman & Diu 279 Monsoon and post-
monsoon
33. UT Delhi 13089 Monsoon and post-
monsoon
34. UT Jammu &
Kashmir
1709 Summer
35. UT Lakshadweep 1 (lowest) Post-monsoon

38
36. UT Puducherry 1625 Post-monsoon
Table 3.4: Overall Incidence of dengue in India across different climates (Mutheneni et
al., 2017; Kakarla et al., 2019; Kakarla et al., 2020):
3.6. Preventive strategies used to control dengue infection in India:
3.6.1. Surveillance system in India:
To combat infection transmission, surveillance is established in the country at the national,
state and district levels by NCVBDC and IDSP. Out of the thirty-eight articles included in the
study, seven articles from January 1st
2010 to June 30th
2022, related to dengue surveillance
in India were scoped. All seven articles focused on the surveillance undertaken by national
government programs such as the NCVBDC and IDSP in the India particularly in the states
of Maharashtra, Andhra Pradesh and Tamil Nadu and addressed the implementation and
strengths, limitations, and overall performance of the surveillance system (Gupta, Ballani,
No. Months Climatic conditions Dengue transmission
1. January Winter Low incidence
2. February Winter Low incidence
3. March Summer Low incidence
4. April Summer Low incidence
5. May Summer Low incidence
6. June Monsoon Increased incidence
7. July Monsoon Increased incidence
8. August Monsoon Peak rise in the incidence (due to
rain or dry climate)
9. September Monsoon Peak rise in the incidence (due to
rain or dry climate)
10. October Post-Monsoon Low incidence
11. November Post-monsoon Low incidence
12. December Post-monsoon Low incidence

39
2014; Gupta, Reddy, 2013; Pilot et al., 2020; Nittas et al., 2019; Chandran, Azeez, 2015;
Ramdas, Nair, 2020; Phalkey et al., 2013).
The outcome of the studies indicates that these surveillance systems are effective in
controlling and containing dengue infection across the country. However, a more systematic
approach is yet to be established to utilise them to their full potential (Pilot et al., 2020; Nittas
et al., 2019). The layout and functions of the surveillance system from the selected studies are
summarised in flowchart 3.2.
Flowchart 3.2: Organisation of the surveillance system of India (Pilot et al., 2020; Nittas
et al., 2019; Gupta, Ballani, 2014; Gupta, Reddy, 2013)
3.7.2.
Ministry of Health and Family Welfare (MoHFW)
(India)
National Center for Vector-Borne Disease
Control (NCVBDC): Program used to
monitor and control vector borne disease
like dengue.
Integrated Disease Surveillance Programs
(IDSP): Program used to identify index cases
and outbreaks of communicable diseases like
dengue.
National
Unit
State
Unit
District
Units
Community
& Primary
Health
Centres
Central
Unit
State
Unit
District
Unit

40
3.6.2. Vector Control:
Out of the thirty-eight studies selected, six articles from January 1st
2010 to June 30th
2022,
related to vector control in India were scoped. Three articles focused on the general control
measures in the form of behavioural practices and chemical and biological vector control
adopted by the Indian public health system to eliminate vector breeding grounds (Gupta,
Ballani, 2014; Gupta, Reddy, 2013; Paradhkar et al., 2021). Two articles focused on the plant
based insecticides and its efficiency (Govindarajan, Sivakumar, 2014; Gosh et al., 2012). One
article focused on the preventive measures adopted in Kolkata, West Bengal and its success
in controlling the infection (Bal, Sodoudi, 2020).
The outcome of the studies showed that behavioural practices were the primary interventions
and were able to prevent the infection to an extent (Gupta, Ballani, 2014). However, there is a
need for secondary interventions like insecticides (Gupta, Ballani, 2014; Gupta, Reddy,
2013). Therefore, plant-based compounds are being used as they are more environmentally
friendly than chemical-based compounds and have started becoming popular in the Indian
market (Govindarajan, Sivakumar, 2014; Gosh et al., 2012). Another key finding is that in
many Indian states surveillance and vector control are integrated together to prevent and
control dengue infection in an ideal manner (Gupta, Ballani, 2014; Gupta, Reddy, 2013). The
key findings from the selected studies are summarised in table 3.5.
Table 3.5: Vector control measures in India:
Vector control measure Components Functions and success
Behavioural practices (Gupta,
Ballani, 2014)
Mosquito nets, repellents Primary protection against vectors,
provides minimal protection.
Chemical-based compounds (Gupta,
Ballani, 2014; Gupta, Reddy, 2013)
DDT, temephos, dieldrin,
pyrethroids
Integrated with the surveillance
systems in India, commonly used and
proven to be highly effective.
Biological-based compounds
(Govindarajan, Sivakumar, 2014;
Gosh et al., 2012)
Plant extracts from Eclipta
alba, Erythrina indica,
New compounds are biodegradable
and have a less negative impact on
humans; therefore, they have recently

41
Cipadessa baccifera, and
Asparagus racemosus.
been integrated with the surveillance
programs in India and have proven
effective in curbing dengue.
Rare practices (Gupta, Reddy,
2013; Paradhkar et al., 2021)
Wolbachia-based dengue
control, insects with
dominant lethal gene and
peri domestic thermal
fogging.
Research is still in the initial phases,
and success has not yet been
determined in its total capacity in the
Indian scenarios.
3.6.3. Community education programs:
Out of the thirty-eight articles included, six articles from January 1st
2010, to June 30th
2022
related to community education programs about dengue prevention and control in India were
scoped. Two articles focus on the benefits of community education programs in India (Gupta,
Reddy, 2013; Paradhkar et al., 2021). Four articles focus on community education programs
implemented in Delhi, Kerala, and Rajasthan and how it has efficiently controlled dengue
infection and have proven to be an immense success at grassroots levels (Gopalan et al.,
2021; Yadlapalli et al., 2017; George et al., 2017; Mathur et al., 2020). The key findings from
the selected studies are summarised in table 3.6.
Table 3.6: Community education programs in three major states of India:
Indian States Community program Success
Alappuzha district, Kerala
(Gopalan et al., 2021)
Community committee with
vector control and reduction
activities with community
participation.
Immense success
Ernakulam district, Kerala
(George et al., 2017)
Behaviour change
communication (BCC)
instils a positive attitude in
the community.
Very effective.
Delhi (Yadlapalli et al.,
2017)
Health education regarding
personal protective measures
Very effective.

42
in association with
municipal bodies and NGOs.
Rajasthan (Mathur et al.,
2020)
Pamphlets and counselling Slow success
3.6.4. Dengue Vaccines:
Out of the thirty-eight articles included in the study, six articles from January 1st
2010 to June
30th 2022 related dengue vaccine development in India were scoped. The articles focus on
vaccine research, development, and rollout in India and indicate that several vaccines are
being developed and undergoing trials by different Indian pharmaceutical companies for use
in the Indian community (Gupta, Reddy, 2013; Gupta, Ballani, 2014; Khetarpal, Khanna,
2016; Swaminathan, Khanna, 2019; Ramasamy et al., 2018; Paradhkar et al., 2021).
Key findings from the studies suggest that currently, the indigenous vaccine DSV4 is under
trials along with live attenuated chimeric yellow fever dengue virus vaccine (Swaminathan,
Khanna, 2019; Ramasamy et al., 2018). Both these vaccines are produced by Indian
pharmaceutical companies. There are several vaccine candidates undergoing trials in India
(Swaminathan, Khanna, 2019; Gupta, Ballani, 2014). The classification of dengue vaccines
obtained from the selected studies has been organised into flowchart 3.3.

43
Flowchart 3.3: Types of Dengue vaccines (Khetarpal, Khanna, 2016)
3.5.5. GIS Mapping:
Out of the thirty-eight articles included in the study, five articles from January 1st
2010, to
June 30th
2022 related to GIS mapping of dengue cases in India are scoped. three articles
focus on the general purview of GIS mapping and its efficiency in India and indicate that the
new technology is being employed to track and control infection through geospatial analysis
(GIS mapping) (Paradhkar et al., 2021; Gupta, Reddy, 2013; Singh et al., 2022). Two articles
focus on GIS mapping in Delhi and Telangana and how it has been able to track infections in
the state (Singh, Chaturvedi, 2021; Gandhi et al., 2017).
The outcomes of the studies suggest that it is quite an efficient method to monitor infections
however the government has not utilised it to its full potential (Singh, Chaturvedi, 2021;
Dengue
vaccine
Replicating dengue viral
vaccines
Cell
cultures
Vaccine
by
mutage
nesis
Chimeri
c
vaccines
Live attenuated
dengue vaccines
(LAV)
Recombina
nt subunit
proteins
Vector
vaccine
Virus
like
particle
vaccine
Inactivated
virus
DNA
vaccine

44
Gandhi et al., 2017). The key findings from the selected studies have been summarised in
table 3.7.
Table 3.7: GIS mapping in two states of India:
Indian States GIS mapping Success
Delhi (Singh, Chaturvedi,
2021)
GIS technology is based on
age, season, and gender
Effective in identifying
dengue hotspots in several
districts of Delhi
Telangana (Gandhi et al.,
2017)
Epidemiology GIS and GPS,
remote sensing data
Effective in identifying
dengue hotspots in villages

45
Chapter 4: Discussion
4.1. Incidence of dengue in India:
4.1.1. Incidence of dengue according to DENV serotypes:
DHF was a rare infection in India before the 1990s despite all the risk factors (Gupta et al.,
2012). However, in the last six decades, dengue has been a rapidly spreading infection, and
there have been profound changes in the epidemiology of the infection based on the common
serotypes, spatial and climatic parameters, and the severity of the disease (Kakarla et al.,
2020; Mutheneni et al., 2017). The first outbreak of dengue fever was in Chennai in 1780, but
the first recorded case was in 1946 (Gupta et al., 2012). In 1944, the virus was first isolated
from serum samples of US soldiers in Kolkata (Gupta et al., 2012). For the next 18 years,
there was no sign of dengue infections in the country (Gupta et al., 2012). The first
laboratory-confirmed epidemic was on the Indian East coast, specifically in Kolkata in 1963,
reaching Delhi and Kanpur in 1967 and 1968, respectively (Kakarla et al., 2020). The first
recorded significant epidemic was observed in Delhi and Lucknow in 1996, gradually
spreading to various parts of the country (Kakarla et al., 2020). Dengue virus has four
serotypes- DENV1, DENV2, DENV3 and DENV4 (Mutheneni et al., 2017). In 1968, all four
serotypes were observed and isolated in Vellore (Gupta et al., 2012). Various contributing
factors have led to the increased incidence of dengue in India, like rapid urbanisation,
lifestyle changes, inappropriate water storage practices, globalisation, and extensive travel
(Kakarla et al., 2020). Since 2010 there has been a rapid rise in the cases, with approximately
200,000 cases reaching in 2018 (Kakarla et al., 2020).
A. DENV 1:
In 1956, the serotype was first isolated in Vellore, Tamil Nadu (Roy, Bhattacharjee, 2021).
From 1996-1997, DENV 1 was observed in the Delhi region and from 2001-2007, it was
observed in Delhi and Gwalior (Roy, Bhattacharjee, 2021). A current study shows that the
strain is predominant in Assam, Nagaland, Himachal Pradesh, Kerala, and Karnataka
(Alagarasu et al., 2021).
B. DENV 2:
DENV 2 was isolated in India from 1956 to 2011 and the infection was observed for the first
time in Vellore in 1964 (Gupta et al., 2012). The infection outbreak in Kanpur from 1968-
1969 was due to DENV 2, followed by infection in the adjacent city of Hardoi, Uttar Pradesh,

46
in 1970 (Roy, Bhattacharjee, 2021). The circulation of DENV 2 expanded to the Southern
regions of Kerala in 1974 (Alagarasu et al., 2021). In 1975, the DENV 2 infection was
observed in Maharashtra and in 1988, infection occurred in parts of Delhi and Gujarat
(Ganeshkumar et al., 2018). Mangalore city of Karnataka observed rising cases of DENV 2 in
1993 (Ganeshkumar et al., 2018). In 1996, Lucknow, Delhi and rural areas of Haryana saw
increasing patients with DENV 2 (Roy, Bhattacharjee, 2021). Southern states of Andhra
Pradesh in 2000 and Dharmapuri city of Tamil Nadu in 2001 saw a rise in DENV 2 cases
(Alagarasu et al., 2021). In 2001, there were DENV 2 cases in Gwalior and Madhya Pradesh
and in 2002, saw an increase in cases in Punjab (Ganeshkumar et al., 2018). In 2005, several
cases were observed in Siliguri, West Bengal (Roy, Bhattacharjee, 2021). There have been
cases of DENV 2 in the North-Eastern regions of Assam and Nagaland and the union
territories of Andaman and Nicobar Islands (Chetry et al.,2019). The North-Eastern areas of
Meghalaya and Mizoram have experienced a rise in cases in 2016 and 2018, respectively
(Chetry et al., 2019). Currently, DENV 2 is common in Uttar Pradesh, Gujarat, Rajasthan,
Jharkhand, Odisha, Andhra Pradesh, Telangana, Tamil Nadu, and Puducherry (Alagarasu et
al., 2021).
C. DENV 3:
In 1966, the DENV3 serotype was prevalent in the Vellore epidemic (Gupta et al., 2012).
There were rising DENV 3 infections in Kolkata in 1983 and 1990 and Jalore town in
Rajasthan in 1985 (Roy, Bhattacharjee, 2021). In 2001, DENV 3 infections were observed in
Chennai and in 2003, cases were reported in Delhi, Gwalior, Pondicherry, and Kanyakumari
(Alagarasu et al., 2021). Infections were seen in Kolkata (West Bengal) in 2005, a re-
emergence in Delhi in 2006 and increased incidence in rural areas of Madurai (Tamil Nadu)
in 2007 (Roy, Bhattacharjee, 2021). Currently, DENV 3 is prevalent in Haryana and Madhya
Pradesh (Alagarasu et al., 2021).
D. DENV 4:
DENV 4 infections were observed, showing a change in the trends of dengue virus
transmission (Gupta et al., 2012). The Kanpur epidemic in the 1960s saw the first case of
DENV 4 in India (Gupta et al., 2012). In 2009 and 2010, there were DENV4 infections in
Pune (Roy, Bhattacharjee, 2021). Currently, this strain is particularly dominant in the Union
territory of the Andaman and Nicobar Islands (Alagarasu et al., 2021).

47
E. Coinfections of DENV serotypes:
Several coinfections have been combined with different serotypes (Gupta et al., 2012). The
first coinfection was observed in 1968 in Vellore by DENV 1, 2, 3 and 4 (Gupta et al., 2012).
Similar coinfections were observed in 1969 in Kanpur and Rajasthan by DENV 2 and 4 and
DENV 1 and 3, respectively (Roy, Bhattacharjee, 2021). In 1982 and 1989, coinfections were
recorded in Delhi and the Parbhani district of Maharashtra by DENV 1 and 2 (Roy,
Bhattacharjee, 2021). Ludhiana (Punjab) reported a coinfection in 1996 by DENV 1,2,3, and
4 (Ganeshkumar et al., 2018). The Indian capital of Delhi has recorded several coinfections
since 2003 caused by several combinations of the serotypes (Ganeshkumar et al., 2018). In
2003, the coinfection was caused by DENV 1, 2, 3 and 4, in 2005 coinfection by DENV 2
and 3, in 2006 by DENV 1, 3 and 4, and from 2007 to 2009 by DENV 1, 2, 3 and 4
(Ganeshkumar et al., 2018). The north-eastern states of Manipur witnessed a coinfection by
DENV 1,2, 3 and 4 in 2007 and in Assam by DENV 1 and 2 in 2015 (Chetry et al., 2019).
In 2007, the coinfection in Andhra Pradesh was caused by DENV 1 and in 2008, Kerala
recorded coinfections by DENV 2 and 3 (Ganeshkumar et al., 2018). In the Northern states of
Uttar Pradesh, from 2009 to 2012, the coinfection was caused by DENV 1, 2 and 3 and in
2015, in Arunachal Pradesh, coinfection was caused by DENV 1, 2 and 4 (Roy,
Bhattacharjee, 2021). In the North-eastern state of Assam, coinfections were recorded in
2016 and 2017 caused by DENV 1, 2 and 3 (Chetry et al., 2019). In two other North-eastern
states, Nagaland and Mizoram, coinfections were caused by DENV 1, 2 and 3 in 2017
(Chetry et al., 2019). The southern state of Karnataka observed a coinfection from 2012 to
2016 by DENV 1,2 and 3 (Ganeshkumar et al., 2018). The most recent coinfection in 2019
and 2020 was observed in Northwest Bengal and caused by all four serotypes (Roy,
Bhattacharjee, 2021). A study done suggested that DENV 1 and 2 are codominant in Punjab,
DENV 1 and 3 are codominant in Maharashtra, and several other serotype infections are
predominant in Andhra Pradesh, Telangana, Tamil Nadu, Gujarat, Jharkhand, Rajasthan, and
West Bengal at the present (Alagarasu et al., 2021).
All this data from different studies suggest that the dengue infection is very diverse in India,
and each dengue serotype has a regional prevalence and has expanded rapidly across the
country since the 1960s. Furthermore, the studies indicate that DENV 2 is the predominant
serotype across the country and there are several coinfections recorded over the years which

48
suggest that immediate action must be taken regarding prevention and treatment (Roy,
Bhattacharjee, 2021; Alagarasu et al., 2021; Gupta et al., 2012).
4.1.2 Incidence of dengue in India based on the prevalence of vectors and incidence
rate:
Dengue is prevalent in India due to factors like rapid urbanisation, globalisation, poor
infrastructure, and climatic conditions which are favourable for vector breeding (Bhatia et al.,
2022). The prevalence of the different species of Aedes mosquitoes differs by their habitat
preference (Bhatia et al., 2022). Mosquitoes are more prevalent in residential areas with high-
density residential homes with inadequate drainage facilities for collecting surface water
runoff indicating a link between improper drainage and dengue transmission (Bhatia et al.,
2022). Concrete or garbage obstructions can prevent the flow of water and causes stagnation
which is a favourable habitat for mosquito species like Aedes aegypti (Bhatia et al., 2022).
Climatic condition like the monsoon is also a suitable habitat for Aedes aegypti breeding due
to the excess stagnant water and wetlands (Mutheneni et al., 2017). However, it is also
prevalent in urban regions with water scarcity, dry climates, or low precipitation conditions,
where water is stored in uncovered water containers (Bhatia et al., 2022). Future projection
models suggest that climate change will be the essential factor in the increased expansion of
Aedes aegypti in the 2050s, such as increased maximum and decreased minimum
temperatures (Bhatia et al., 2022; Mutheneni et al., 2017). In contrast, Aedes albopictus
depends more on precipitation and high temperatures and there will be no modifications in
the habitat of Aedes albopictus in the future years (Hussein, Dhiman, 2022).
According to the distribution maps, Aedes aegypti is prevalent in Kashmir valley, Punjab,
Haryana, Gujarat, Brahmaputra valley, Uttar Pradesh, Delhi, Bihar, West Bengal, and the
southern peninsular regions (Hussein, Dhiman, 2022). Aedes albopictus is prominent in the
Malabar coast, Coromandel coast, Konkan coast, and Western Ghats (Hussein, Dhiman,
2022). However, both vectors are prevalent in the north-eastern areas (Hussein, Dhiman,
2022).
Coming to the incidence rates, recent data released by NCVBDC suggests that the highest
number of cases were from the Northern states of Uttar Pradesh with 29,750 cases, followed
by Punjab, Rajasthan, Delhi, Haryana, Gujarat, Madhya Pradesh, and Maharashtra with more
than 10,000 cases in each state/ union territory (NCVBDC, 2021). A study suggests that
dengue incidence is higher in the country's southern states, especially in Kerala (Mutheneni et

49
al., 2017; Kakarla et al., 2020). However, according to NCVBDC, each of the southern states
reports less than 8000 cases (NCVBDC, 2021), which could be due to the underreporting of
the cases in these regions by the surveillance systems (Mutheneni et al., 2017). The lowest
incidence of dengue was observed in Lakshadweep with one case, followed by Arunachal
Pradesh, Nagaland, Mizoram, Assam, Meghalaya, Andaman and Nicobar Islands with less
than 200 cases in each state/ union territory (NCVBDC, 2021).
Therefore, from the data gathered from the selected studies, the incidence of dengue fever in
India can be categorised based on serotypes, vectors, and regional incidence rates (Mutheneni
et al., 2017). The studies indicate that Aedes aegypti is the predominant vector that transmits
dengue in India (Hussein, Dhiman, 2022) and the infection is concentrated more in the
Northern regions according to the surveillance systems (NCVBDC, 2021) despite few studies
suggesting that the Southern regions have a high incidence (Mutheneni et al., 2017; Kakarla
et al., 2020). According to the NCVBDC, the lowest incidence is observed in the northeastern
regions which is further proved by studies conducted in those regions (NCVBDC, 2021;
Chetry et al., 2018).
Table 3.2 in the results chapter has summarised the incidence of dengue infection in India based
on historical dates, past and current incidence of the four dengue serotypes, and the mosquito
vectors and Table 3.3 shows the incidence rate of dengue infection in India's 28 states and 8
union territories.
4.2. Effect of Indian climate on dengue transmission:
India has complex geographical and climatic conditions and is defined by four seasons:
winter, summer, monsoon and post-monsoon (Bajwala et al., 2020). According to the Indian
Meteorological Department, during January and February, the country mostly experiences
winter; from March to May, it is a pre-monsoon season; from June to September, it is
monsoon; and from October to December, it is post-monsoon (Bajwala et al., 2020). Studies
have suggested a correlation between climatic parameters and dengue transmission and viral
replication (Bal, Sodoudi, 2020; Mutheneni et al., 2017; Pramanik et al., 2020). Additionally,
El Nino and La Nina phenomena influence the country’s monsoon season and a relationship
between summer and rainfall index (Pramanik et al., 2020; Kakarla et al., 2019). The Indian
El Nino is the phenomenon where the Indian ocean gets warmer in the western part and
colder in the eastern region due to the irregular sea surface temperatures (Pramanik et al.,
2020) and causes a dry climate across the country (Kakarla et al., 2019). In contrast, La Nina

50
is the phenomenon where the sea surface temperature is colder in the same region and causes
excess rainfall across the country (Kakarla et al., 2019). These phenomena occur every two to
seven years (Kakarla et al., 2019). A study showed that in 2015 and 2016, the most
significant number of dengue cases were positively correlated to the largest El Nino and La
Nina events in India, which suggests that high temperature and excess rainfall are the main
contributors to dengue transmission (Kakarla et al., 2019).
An increased number of dengue cases are observed from June to September, with a peak rise
in August and September, proving that rainfall contributes to increased dengue incidence
(Kakarla et al., 2019). Table 3.4 in the results section summarises the effect of climate on
dengue transmission in India during the different months of the year. Furthermore, the Indian
climate data from 1980 to 2017 suggested an increased dengue incidence in South and
Central India than in North India and is most prominently seen during the Indian monsoon
period (June to September) (Kakarla et al., 2020). The Intergovernmental Panel on Climate
Change (IPCC) has suggested that globally billions of people are at risk of acquiring dengue
infection by 2080 due to climate change, which shows a direct correlation between dengue
transmission and climatic conditions (Kakarla et al., 2019). All these data suggest that dengue
transmission in India is positively correlated with different climatic conditions (Mutheneni et
al., 2017; Kakarla et al., 2020).
4.2.1. Temperature:
In India, temperature variations are often observed in different climatic zones, and these
variations can influence dengue transmission, viral replication, vector-pathogen interaction,
and incubation period (Mutheneni et al.,2017). Temperature is critical in dengue
transmission, vector growth and expansion (Bhatia et al., 2022). The optimal temperature for
dengue transmission is 16 ℃ to 30 ℃ (Singh et al., 2022). A study suggests that a temperature
range of 17℃ to 30℃ increases dengue transmission by four times (Mutheneni et al., 2017).
Dengue fever has shown the highest incidence when the temperature reaches more than 30 ℃
and at a minimum temperature range of 21 ℃ -24 ℃ (Mala, Jat, 2019). The warm phase of
El Nino Southern Oscillation (ENSO,) which causes extensive summers and dry climates also
correlates with increased dengue transmission (Pramanik et al., 2020).
Temperatures between 24℃ and 32℃ affect the mosquito biting and transmission rate, EIP,
and vector density per host (Kakarla et al., 2020). The elevated temperatures increase the
vector density per host, quicken the biting frequency and therefore make the human-to-

51
mosquito and mosquito-to-human transmission faster (Kakarla et al., 2020). However, the
warm temperatures inversely correlate with the extrinsic incubation period (EIP) that is, EIP
shortens as the temperatures rise (Mutheneni et al., 2017). For instance, a five-day reduction
in EIP leads to three times the dengue transmission rate (Mutheneni et al., 2017). EIP has
been considered an essential entity in the dynamics of dengue transmission since the 1900s,
and it is the viral incubation interval between the period when the mosquito feeds on infected
blood and when the mosquito becomes infected (Mutheneni et al., 2017). EIP is eight to
fourteen days (Mutheneni et al., 2017). Elevated temperature impacts the EIP by increasing
the vector population and competence by affecting the egg laying and hatching of the Aedes
mosquitoes and altering the vector development, resulting in faster viral replication and
transmission (Mala, Jat, 2019; Bhatia et al., 2022). It also affects the mortality, body size,
biting habits and metabolism of the Aedes mosquitoes (Mutheneni et al., 2017; Bajwala et al.,
2020; Bhatia et al., 2022).
A maximum temperature of more than 25 ℃ is observed in the country's Northwest regions
and eastern coast, increasing the dengue incidence in those regions (Pramanik et al., 2020).
There was a correlation between increased dengue transmission and mean maximum
temperature in the country's West, North and Central states (Singh et al., 2022). Increased
dengue cases are observed in the Northern states and union territories after a high summer,
whereas there is an increased incidence in Northeastern and Jammu & Kashmir during
summer (Pramanik et al., 2020). However, there is a negligible impact of summer on the
dengue incidence in Union territories like Daman and Diu, Puducherry, and the eastern coast
(Pramanik et al., 2020). A study suggests that there has been an increase in the temperatures
in the cold Himalayan regions due to climate change which has led to increased dengue cases
in the area (Kakarla et al., 2020).
In contrast, temperatures lower than 20 ℃ decrease dengue transmission in the country
(Bajwala et al., 2020). The national dengue incidence declines during winter (Kakarla et al.,
2020). A minimum temperature of less than 4 ℃ is observed in parts of the North-eastern
areas and Jammu and Kashmir (Mutheneni et al., 2017). There is a negative correlation
between dengue cases and the mean minimum temperature observed in the eastern regions
(Singh et al., 2022). In a study conducted in Delhi, decreased temperatures from October to
December gradually decreased dengue incidence (Mala, Jat, 2019). However, one study in
Maharashtra shows that when the maximum temperature declined, there was an increased
incidence of dengue cases in that area (Patil, Pandya, 2021). Another study shows that a

52
temperature drop during monsoon impedes water evaporation in water bodies and provides an
excellent vector habitat for Aedes larvae and pupae (Bajwala et al., 2020). The wind is also a
contributing factor to dengue incidence as a mean increasing wind speed range of 4 to 6 km/h
increases the incidence (Mala, Jat, 2019). However, these studies do not indicate that
minimum temperature or wind is the lone contributing factor as there are other factors, such
as urbanisation, travelling and water storage practices that may have contributed to the rise in
infection (Mala, Jat, 2019; Patil, Pandya, 2021).
Therefore, the information gathered from these studies indicates that elevated temperatures
have a linear relationship with dengue transmission and viral replication and affect the EIP
and the mosquito breeding habitats (Mutheneni et al., 2017; Bal, Sodoudi, 2020; Kakarla et
al., 2020). The studies also suggest that during summer the infection is prevalent across the
country due to the favourable climatic conditions (Pramanik et al., 2020; Singh et al., 2022).
In contrast, the winter season is not favourable for mosquito breeding and therefore the
incidence of dengue drops across the country (Mala, Jat, 2019).
4.2.2. Precipitation and Humidity:
Precipitation and humidity contribute to the excess breeding grounds for mosquito vectors
and enhance viral replication (Mutheneni et al., 2017; Bal, Sodoudi, 2020). A study suggests
mosquitoes expand their spatial range, facilitating dengue transmission when favourable
precipitation factors are present (Mutheneni et al., 2017). Overall analysis done by a study in
2017 indicated that there is a moderate to strong positive correlation between dengue
transmission and precipitation (Mutheneni et al., 2017). There is a positive correlation
between precipitation and dengue cases in the east and northeastern regions (Singh et al.,
2022). However, excess precipitation also negatively correlates with dengue transmission as
it can flush out the immature stages of the mosquitoes (Singh et al., 2022).
High humidity contributes to the long life of mosquitoes, shortens the EIP, fastens viral
replication, enhances mosquito biting activity, and causes better virus transmission
(Mutheneni et al., 2017). This facilitates infected female mosquitoes to complete more than
one viral replication cycle (Kakarla et al., 2019). Humidity is observed more during July and
August (Pramanik et al., 2020). In a study done in Kolkata and Orissa, mean humidity
showed a positive relationship with increased dengue cases (Bal, Sodoudi, 2020; Rao et al.,
2018). Another study in Maharashtra shows that relative humidity is a direct cofactor in the
increased incidence of dengue infection (Patil, Pandya, 2021).

53
Therefore, all these studies suggest that humidity and precipitation are major contributing
factors in dengue transmission (Pramanik et al., 2020; Mutheneni et al., 2017). However
excess precipitation is not favourable for mosquito breeding and therefore there is a non-
linear relationship between precipitation and dengue transmission (Singh et al., 2022). In
contrast excess humidity has a linear relationship with dengue transmission as it is a
favourable condition for mosquito breeding (Mutheneni et al., 2017)
4.2.3. Rainfall:
The Indian subcontinent receives 75% of its rainfall from June to September (Mutheneni et
al.,2017) and therefore there is maximum dengue transmission from June to September with a
peak rise in August and September (Kakarla et al., 2020). Overall, there is an increase in
dengue cases across the country during the Indian monsoon season and La Nina phenomenon
(Pramanik et al., 2020). There is a drop in temperature (an average 2 ℃) from June to
September from the beginning of the monsoon to the end of the season. All these conditions
provide ample breeding grounds for Aedes mosquitoes (Kakarla et al., 2020). Overall
analysis done by a study in 2017 indicates that rainfall greater than 1mm or 10mm facilitates
dengue transmission (Mutheneni et al., 2017). Mosquitoes spend their life in stagnant water
before developing into adult mosquitoes, and excess rainfall creates ample breeding grounds
for larvae and pupae growth (Bhatia et al., 2022). Excess rainfall is observed in Eastern states
like Kolkata, western Coast states, and Western Rajasthan (Pramanik et al., 2020). In a study
done in Kolkata, mean rainfall showed a positive relationship with increased dengue cases.
Another study in Maharashtra indicated that excess rain between June and September had
increased dengue incidence (Patil, Pandya, 2021). However, heavy rainfall can wash out
vector breeding grounds, as proved by another study which shows that if rainfall exceeds 80
mm, the dengue incidence decreases (Kakarla et al., 2019).
A study indicates that despite deficit rainfall observed in the Northwest, north-eastern,
northern, west coast, and Jammu and Kashmir (Mutheneni et al., 2017), there is an increased
incidence of dengue (Pramanik et al., 2020). The same is observed in the post-monsoon
season when there is less rainfall, leading to increased dengue cases in the country's
northeastern, eastern, and southern states (Pramanik et al., 2020). This increase in cases could
be due to the dry climate and elevated temperature due to deficit rainfall which are also
favourable for vector breeding (Pramanik et al., 2020). Furthermore, reduced rain due to the
current climate change has caused water scarcity due to improper storage of water in

54
households (Akter et al., 2017). People store water in clay containers without covers and
unprotected reservoirs in their homes, and this water is an excellent breeding ground for
anthropophilic Aedes aegypti and facilitates dengue transmission (Akter et al., 2017; Mala,
Jat, 2019).
Therefore, all these studies conclude that rainfall is essential in dengue transmission in India.
However, there is a non-linear relationship between rainfall and dengue transmission, as these
studies suggest that there may be other factors at play such as improper water storage
practices (Mutheneni et al., 2017; Pramanik et al., 2020; Akter et al., 2017; Mala, Jat, 2019).
So, more research must be undertaken on this aspect of dengue transmission as there are still
gaps in the literature because the Indian research concentrates more on the epidemiological
and entomological aspects of dengue (Bal, Sodoudi, 2020; Mutheneni et al., 2017; Kakarla et
al., 2020). However, the current research on the effects of climatic factors on dengue
transmission has made it possible to develop early dengue forecasting models in the country’s
different regions (Bal, Sodoudi, 2020). Table 3.3 in the results section has summarised the
association between the incidence rate in 28 states and eight union territories of India and
climatic conditions.
4.3. Preventive interventions:
4.3.1. Surveillance:
Surveillance is integral to dengue control and prevention in India (Gupta, Ballani, 2014). The
surveillance is mainly undertaken by sentinel surveillance in association with laboratory tests
conducted by virology labs in different states (Gupta, Reddy, 2013). The laboratory tests
identify the dengue serotype and its genetic components and disease severity, which helps
control the infection (Gupta, Ballani, 2014). Disease surveillance is a challenging task in the
country due to the complex monitoring of cases, control of epidemics and the economic
impact of the epidemics (Pilot et al., 2020). India has two pillars for disease surveillance in
the form of independent national programs such as NCVBDC and IDSP (Pilot et al., 2020).
One hundred seventy sentinel hospitals and 13 apex referral laboratories are established in the
endemic states of the country (Gupta, Reddy, 2013). The national administrative section has
multiple layers in the form of national, state, district, and local municipal wards (Pilot et al.,
2020). The implementation of the two national programs depends on the primary and private
healthcare centres, various stakeholders, evidence-based planning and intersectoral
coordination (Pilot et al., 2020). However, there is a lack of cooperation and improper

55
approaches undertaken among the various layers of the program to control infection, limited
integration, and inflexible communication among the different layers (Pilot et al., 2020).
Another challenge of surveillance is the underreporting of the cases due to asymptomatic
cases, patients being unaware of their symptoms, inadequate health facilities and
misdiagnosis (Gupta, Reddy, 2013). Therefore, there is a need for extensive dengue
surveillance to contain the spread of outbreaks (Nittas et al., 2019).
A) National Center for Vector-Borne Disease Control (NCVBDC):
NCVBDC conducts the nation’s vector and disease surveillance and control and was first
established for malaria prevention but later focused on other vector-borne diseases like
dengue and chikungunya (Gupta, Reddy, 2013). The structure of NCVBDC is divided into
different subunits at the district level, headed by each subunit head officer (Nittas et al.,
2019). These units are divided into sectors and sections led by health supervisors and health
assistants (Nittas et al., 2019). There are active agents and passive agents in NCVBDC.
Active agents are involved in fieldwork but do not work on the blood samples, while passive
agents work in hospitals collecting samples from the patients and testing them (Pilot et al.,
2020). The organisation of NCVBDC is summarised in flowchart 3.2 in the reports section.
The reporting is based on a laboratory-confirmed case from sentinel laboratories, and
suspected dengue cases are referred to laboratories with advanced facilities (Chandran,
Azeez, 2015). Reporting by NCVBDC takes place via electronic mode on a daily and weekly
basis and is then prepared by different states and district units monthly (Chandran, Azeez,
2015). Other than reporting, NCVBDC controls the primary health interventions and
community programs, implementing dengue control measures to contain outbreaks in the
form of clinical surveillance and home-based blood sample collection (Gupta, Reddy, 2013).
There are a few limitations of NCVBDC, such as restricted reporting by a network of sentinel
laboratories excluding primary, secondary and private health facilities, which leads to
underreporting of the cases and causes a challenge for disease surveillance (Gupta, Reddy,
2013). Additionally, there are insufficient efforts to expand the skills of healthcare field
workers and a lack of modern technology (Pilot et al., 2020). Despite the challenges, the
surveillance system by NCVBDC is still considered the most effective strategy for preventing
and controlling dengue infection in India as it is extensively connected by different health
units and diagnostic laboratories all over the country (Pilot et al., 2020).

56
B) Integrated Disease Surveillance Program (IDSP):
IDSP is a decentralised active and passive surveillance system that uses one infrastructure to
track dengue and other communicable diseases (Ramdas, Nair, 2020). IDSP has state
surveillance units (SSU) located in all the districts of the state and receives reports from
primary health centres (PHC), community health centres (CHC), dispensaries, public and
private hospitals, and an institute for community health (Pilot et al., 2020). There are around
35 SSUs and 604 district surveillance units (DSUs) that report to the National Center for
Disease Control (NCDC) in Delhi (Phalkey et al., 2013). Each office has four central
positions and is headed by the district surveillance officer. The office also has one
epidemiologist, one data operator and one data manager (Phalkey et al., 2013). The office has
outsourced four other data operators to different government tertiary health units undertaking
sentinel surveillance (Pilot et al., 2020). The layout of IDSP is summarised in flowchart 3.2
in the results section.
The main component of IDSP is reporting from health care units ranging from primary care
centres to tertiary hospitals (Ramdas, Nair, 2020). The reports are categorised into three
groups: Suspected or S forms completed by nurses or midwives undertaking primary health
work, presumptive or P forms completed by district medical officers and laboratory-
confirmed or L forms completed by laboratory professionals (Phalkey et al., 2013). After
reporting and categorising the cases, dengue cases are confirmed via a network of virology
laboratories integrated with tertiary health units, excluding PHC (Nittas et al., 2019). The
next step is an analysis carried out by the epidemiologist, district medical officer and data
operator utilising the L forms and geographical and meteorological parameters (Chandran,
Azeez, 2015). IDSP has reported dengue cases the most out of all the communicable diseases
constituting 70.6% (Ramdas, Nair, 2020).
The limitation of reporting in the IDSP is the inaccuracy of the data and gaps in reporting the
cases, especially the suspected and presumptive cases where incomplete patient details are
filled (Nittas et al., 2019). One factor contributing to underreporting of cases is fear among
the healthcare staff to report the actual number of patients due to negative feedback from the
head of the department (Nittas et al., 2019). Additionally, there is underreporting of cases
from private health centres, which contributes to insufficient data (Gupta, Reddy, 2013). The
second factor is the burdensome paperwork associated with incomplete case reporting (Pilot
et al., 2020). The limitation for confirmation of patients is the limited number of laboratory

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