This document discusses an upcoming presentation on outbreak investigation. It begins with definitions of key terms like epidemic, outbreak, endemic, and pandemic. It then discusses determinants of disease outbreaks and types of epidemics. The objectives, steps, and examples of outbreak investigation are provided. Various factors related to outbreaks like incubation period, quarantine, herd immunity, and triggers for surveillance are defined.

1. Presented by: Dr. Timiresh Kumar Das
Moderator: Dr. Neelam Roy
Associate Professor
Dept. of Community Medicine
VMMC & Safdarjung Hospital

2.  Definitions
 Determinants of disease outbreaks
 Types of epidemics
 Objectives of investigation of outbreak/ epidemic
 Steps of outbreak investigation
 Some examples
 References

3.  Epidemic: [Greek: epi (upon) demos (the people)]

The occurrence in a community or region of cases of an
illness, specific health related behaviour, or other health
related events clearly in excess of normal expectancy.1
A Dictionary of Epidemiology – 3rd ed; Last JM. 2000.

The “unusual” occurrence in a community or region of
disease, specific health related behaviour, or other health
related events clearly in excess of “expected occurrences”.2
Park’s Textbook of Preventive and Social Medicine – 21st ed; Park JE. 2010

The occurrence in a community or region of a group of
illnesses of similar nature, clearly in excess of normal
expectancy, and derived from a common or from a
propagated source.3
Epidemiology – 4th ed; Gordis L. 2004

4.  Outbreak:

An epidemic limited to a localised increase in the incidence
of a disease, e.g., in a village, town, or closed institution. (=
upsurge)1
A Dictionary of Epidemiology – 3rd ed; Last JM. 2000.

A term used for a small, usually localised epidemic in the
interest of minimising public alarm.2
Park’s Textbook of Preventive and Social Medicine – 21st ed; Park JE. 2010

An outbreak is the occurrence of illness, specific health
related behaviour, or other event clearly in excess of
normal expectancy in a community in a specified time
period. An outbreak is limited or localised to a village,
town, or closed institution.4
Checklist for CRRT for outbreak investigation, NICD 2008

5.  According to the Oxford Textbook of Public Health the criteria for
judging that an outbreak has happened can be one of the
following.5

The occurrence of a greater number of cases or events than normally
occur in the same place when compared to the same duration in past
years.


A cluster of cases of the same disease occurs which can be linked to
the same exposure.


E.g. Kaposi's sarcoma, New York - 30 in 1981; only 2-3 previous yrs.
E.g. 3 athletes admitted with acute febrile illness after triathlon in
Springfield, Illinois. Triathlon related to illness. Leptospira.
A single case of disease that has never occurred before or might have a
significant implication for public health policy and practice can be
judged an outbreak which deserves to be investigated.

E.g. - Avian flu (H5N1) Hong Kong in a 3-year boy in May 1997 alerted local
auth. and scientists around the world to start a full-scale investigation.

6.  Endemic: The constant presence of a disease or
infectious agent within a given geographic area or
population group, without importation from outside;
may also refer to the usual or expected frequency of
the disease within such area or population group.
A Dictionary of Epidemiology – 3rd ed; Last JM. 2000.
 Pandemic: An epidemic usually affecting a large
proportion of the population, occurring over a wide
geographic area such as a section of a nation, the
entire nation, or a continent or the world.
A Dictionary of Epidemiology – 3rd ed; Last JM. 2000.

7. SUSCEPTIBLE
DISEASE
OUTBREAK
IMMUNE
NO
OUTBREAK
 When formerly isolated populations are exposed to disease.
19th century – measles in Faroe islands.
 When susceptible population is introduced to an endemic
area – streptococcal sore throat outbreaks when new recruits
arrived at Great Lakes Naval Station, USA.

8.  Herd Immunity: The immunity o f a group or
community. The resistance of a group to invasion
and spread of an infectious agent, based on the
resistance to infection of a high proportion of the
individuals members of the group.1
 When a large proportion of the population is
immune, the entire population is likely to be
protected, not only those who are immune.
 Degree depends on –
Extent of random mixing of the population
 Agent and transmission characteristics.
 Environmental factors.
 Number of susceptibles and immunes in the population.


9. 14
12
10
8
Expected number of cases
if effect limited to vaccines
6
REDUCED BY
HERD IMMUNITY
Number of cases observed
4
2
0
1958
1959
1960
1961

10.  Incubation Period: Interval from receipt of infection
to the time of onset of clinical illness.1
Important in case of isolating infected people to prevent
transmission.
 Isolation or quarantine should be greater than maximum
incubation period.
 Useful if disease may be introduced into new areas.


11.  Quarantine: The restriction of activities of well
persons or animals who have been exposed to a case
of communicable disease during its period of
communicability (i.e. contacts) to prevent disease
transmission during incubation period if infection
should occur.1
From quarante giorni (40 days).
 Plague (Black Death) Europe, 1374 – Venetian Republic
 1377, Ragusa detained travellers in an isolated
area, initially for 30 days and, when it did not work, for 40
days


12.  Common-source epidemics
 Single source
or point source epidemics
 Continuous or multiple exposure epidemics
 Propagated epidemics
 Person
to person
 Arthropod vector
 Animal reservoir
 Slow (modern) epidemics

13.  Point Source: A point source outbreak occurs
when there is one single source that exists for a
very short time and all cases have common
exposure to it in that same particular period.
 Ex: food poisoning

14.  Common source single exposure
First case and the last case happen within one
incubation period
 Rapid rise in number of cases followed by rapid decline


Example:
 Food poisoning
due to spoiled food item in a feast.
 Bhopal gas tragedy ( 198

15.  Common source multiple exposure: There is only one
source, which provides continuous or intermittent
exposure over a longer period
 Example:

Prostitute transmitting STD to her clients

Typhoid Mary

Water supply contamination due to leaky pipes.
 Continuous
if leak is constant.
 Intermittent if leak occurs during pressure variations.

16.  Propagated epidemic: This
kind of outbreak is
caused by a transmission from one person to
another person.
 Example: SARS, H1N1 influenza

17. To define the magnitude
 To determine the particular conditions and
factors responsible for the occurrence of the
epidemic
 To identify the cause, source of infection, and
modes of transmission
 To formulate prevention and control measures


18. 






To control the current outbreak.
Prevention of future outbreaks.
Describe new diseases and learn more about known
diseases.
Evaluation of the effectiveness of prevention
programmes.
Evaluation of the effectiveness of the existing
surveillance system.
Training health professionals.
Responding to public, political, or legal concern .

19.  The first person who comes across news
of an outbreak / The health worker/ ANM
 PHC medical officer / the CHC in charge
 The District health officer / District RRT
or DEIT/ State RRT
 Specialized agencies like NCDC (NICD).

20. 1. Verification of the diagnosis
2. Confirmation of existence of outbreak
3. Defining population at risk – Map, Count
4. Rapid search for cases and characteristics
5. Data Analysis – Time, Place, Person
6. Formulation of hypothesis
7. Testing of hypothesis
8. Evaluation of ecological factors
9. Further investigations
10. Reporting

21.  Verify rumours
 Technical, Administrative and Logistics
arrangement
 Prepare Outbreak Management Kit according to
initial information
 Brief members of the investigating team regarding
Roles & responsibilities
 Methods of personal protection

Team composed of:
1. Nodal officer (Epi/ PHS)
2. Clinician
3. Microbiologist
4. Health Assistant
5. District/ Local administration
nominee
6. Other personnel as required

22. 
Verification of the diagnosis is usually made on
clinical and laboratory parameters.
 Ensure that the problem has been properly
diagnosed -- the outbreak really is what it has been
reported to be
 Review
clinical findings and laboratory results for
affected people
 Visit or talk to several of the people who became ill
For outbreaks involving infectious or toxic chemical
agents, be certain that the increase in diagnosed
cases is not the result of a mistake in the
laboratory.

23.  Incidence rate is calculated by dividing the total cases
by the population at risk.
7 ye ar ave rage incide nce vs . 2003 incide nce of D e ngue in
2003
D e lhi
av g
2000
1861
1800
1600
1400
n o . o f c as e s
 This rate is
compared with the
rate occurring in
the same
population, during
the corresponding
period of the
previous years.
1200
1189
1000
800
600
600
0
200
0
0
400
0
0
0
0
0
1
0
0
0
F
M
A
M
J
10
4
J
213
2
1
0
J
15
362
A
months of reporting
148
101
S
O
N
D

24. •
•
•
•
•
Clustering of cases or deaths
Increases in cases or deaths
Single case of disease of epidemic potential
Acute febrile illness of an unknown etiology
Two or more linked cases of disease with outbreak
potential(e.g., Measles, Cholera, Dengue, Japanese
encephalitis or plague)
•
•
•
•
•
•
Unusual isolate (Cholera O 139)
Unusual presentation
Environmental factors e.g. rainfall, climate
Shift in age distribution of cases
High vector density
Natural disasters

25.  Rumour register

To be kept in standardized format in each
institution
 Community informants

Private and public sector
 Media

Important source of information, not to neglect
 Review of routine data – surveillance data

Triggers (There are triggers for each condition under
surveillance, Various trigger levels may lead to local or
broader response)

26.  Threshold for diseases under surveillance that trigger pre-
determined actions at various levels
 Based upon the number of cases in weekly report
 Trigger levels depend on:
 Type of disease
 Case fatality (Death / case ratio)
 Number of evolving cases
 Usual trend in the region

27. Trigger
Significance
Levels of response
1
Suspected /limited outbreak
• Local response by health
worker and medical officer
2
Outbreak
• Local and district response
by district surveillance
officer and rapid response
team
3
Confirmed outbreak
• Local, district and state
4
Wide spread epidemic
• State level response
5
Disaster response
• Local, district, state and
centre

28.  Examples:

Trigger levels for Dengue
 Trigger
1
• Clustering of 2 similar case of probable Dengue fever in a village
• Single case of Dengue hemorrhagic fever
 Trigger
2
• More than 4 cases of Dengue fever in a village 1000 population.

Triggers for syndromic surveillance
 Fever
• More than 2 similar case in the village (1000 Population)
 Jaundice
• More than two cases of jaundice in different houses irrespective
of age in a village or 1000 population

29. Disease alerts/
outbreaks
reported and
responded to by
states/ UTs
through IDSP;
2nd week (ending
15th
January, 2012)

30. • Severity of illness
• Number of cases
• Source / mode of transmission
• Availability of preventive & control measures
• Availability of staff & resources
• Public, political and legal concerns
• Public health program considerations
•Potential to affect others if the control
measures are not taken
• Research opportunity

31.  Pseudo-outbreaks:
 Artifact
in the numerator:
 Increased awareness
 Reporting of prevalent cases as incident cases (e.g.;
hepatitis C, sleeping sickness)
 Laboratory error
 Variation of the denominator:
 Rapidly changing population denominators
 Migrants or refugees

32.  Obtain a map of the area
 Counting of the population
 Helps to calculate the denominator for further
calculation of attack rates.
 Provides us with the possible number of people at
risk.
 Mapping helps us to know area: ecological and
environmental factors.

33.  Map :
Detailed, Current map of the area.
 If not available – prepare
 Information: Natural landmarks, Roads, All dwelling
units, Sources of water, Other important features

 Counting:
Census by age and sex
 Lay health workers
 House to house visits


34.  Includes: Framing a case definition, searching for
cases and doing a epidemiological survey.
 A case definition is a standard set of criteria for
deciding whether an individual should be classified as
having the health condition of interest.
 Criteria




Clinical and/or biological criteria,
Time
Place
Person
 Case definition should be
balanced, practical, reliable and applied without bias.

35. Example - Measles: 3 definitions
 Fever and runny nose
 Too sensitive
 Too many other illnesses produce same symptoms
 Call many illnesses “measles”
 Fever and rash and Koplik’s spots and conjunctivitis
 Too specific
 Many cases of measles do not have all these signs
 Miss many real cases of measles
 IDSP case definition: Fever of 3-7 days duration, with
generalized maculopapular rashes; with history of cough, coryza,
conjunctivitis or Koplik’s spots.

36.  Suspect -Fewer of the typical clinical features
 Probable- Typical clinical features of the disease
without laboratory confirmation.
 Confirmed- Typical clinical features with laboratory
verification.
Confirmed Case
Laboratory
Verification
++
Possible Case
+
Clinical
Features
Probable Case
++
+

37.  Example: E. coli O157 outbreak at
Restaurant X on 31/3/2010
 Possible: diarrhea (3 loose stools per day) and
ate food purchased at restaurant X on 31/3
 Probable: bloody diarrhea and ate food
purchased at restaurant X during on 31/3
 Confirmed: culture positive with “outbreak”
PFGE pattern and ate food purchased from
restaurant X on 31/3

38.  Case Definition may need to be updated within
an investigation
 Broad to specific
 Infection
with E. coli O157 vs. infection with the outbreak
strain (defined by PFGE pattern)
 Location of exposure
 SARS outbreak (travel
within 10 d of onset):
• In February: China/HK/Hanoi/Singapore
• In April: Toronto, Canada added
• In May: Taiwan added
 Dates of exposure can change
 SARS
outbreak: to meet the case definition-dates of
exposure dependant on location of exposure

39.  The first cases to be recognized are usually only a small
proportion of the total number
 To identify other cases, use as many sources possible

Passive Surveillance - Relies on routine notifications by
healthcare personnel

Active Surveillance - Involves regular outreach to potential
reporters to stimulate reporting of specific conditions;
investigators are sent to the afflicted area to collect more
information
 Contact physician offices, hospitals, schools to find
persons with similar symptoms or illnesses
 Send out a letter, telephone or visit the facilities to collect
information
 Through media alerts asking people to get checked

40. WHY TO SEARCH
Iceberg phenomenon
40

41.  The information is collected by “line listing”.

A line list is like a nominal roll of the cases being reported
to the various health care establishments (like
dispensaries, general practitioners or admitted to the
hospitals)
 Constitutes and updates a database of cases
 Done by hand or by Excel.

43.  The survey team will go for “door to door” survey
in the affected area and ask if any person had
suffered with symptoms fitting into case definition
(Rapid Household Survey)
 If yes, their details were recorded on the
epidemiological case - sheet and required samples
are taken and dispatched to the hospital/ reference
laboratory.
Epidemiological case sheet = Case interview form
 Detailed information from the case relevant to the
disease under study.


44. Information includes:
• Name, Age, Sex, Occupation, Social class
• Time of onset of disease, Signs & Symptoms
• Personal contact at home, work, school
• Travel history, attendance at large gatherings
• History of previous exposure/injections,
• Special events such as parties attended, foods
eaten, and exposure to common vehicles such as
water, food and milk

45.  Active door-to-door collection of information is by
“ Rapid Household Survey”

47.  Characterizing an outbreak by time, place and
person is called descriptive epidemiology.
 Descriptive epidemiology is important because:

What is reliable and informative (e.g., similar exposures)

What may not be as reliable (e.g., many missing
responses to a particular question)

Provides a comprehensive description of an outbreak by
showing its trend over time, its geographic extent (place)
and the populations (people) affected by the disease

48.  Development of
proportional
distribution of cases
according to host
characteristics
(age, race, sex)
or
by exposures
(occupation, leisure
activities, use of
medications, tobacco,
drugs).

49.  Count

Count the cases in each age and sex groups
 Divide

Obtain census denominators for each age and sex groups
 Compare

Estimate the incidence for each:
 Age
group
 Sex group

50.  An attack rate is the proportion of a well-defined
population that develops illness over a limited
period of time, such as during an epidemic or
outbreak
 What are the age and gender specific attack rates?
 What age and gender groups are at highest and
lowest risk of illness?
 In what other ways do the characteristics of the
cases differ significantly from those of the
general population?
Purpose => Identification of sub-group(s) at risk

51. Attack rate of measles by age and
sex, Cuddalore, Tamil Nadu,
India, 2004-2005
Characteristics
Age group
Number of Population
cases
Attack
rate per
100,000
255,755
19.6
51
1,795,383
2.8
Male
48
1,032,938
4.6
Female
Total
50
5+
Sex
0-4
53
1,018,200
5.2
101
2,051,138
4.9

52. 100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
Protestants
Coptic Christians
Muslims
Population
Cases of Botulism
BOTULISM OUTBREAK IN CAIRO, EGYPT - APRIL1993
Weber JT, Hibbs RG Jr, Darwish A, et al. A massive outbreak of type E botulism associated with
traditional salted fish in Cairo. J Infect Dis 1993; 167: 451-454

53. What is the exact period of the outbreak?
What is the probable period of exposure?
Is the outbreak likely common source or
propagated?

54. Drawing the epidemic curve based on time distribution of cases
2. Eyeball
distribution
to choose interval
1. Count cases by
time of onset
3. Finalize

55.  Interpretation of epidemic curve
Shape – type of epidemic
 An early case in the curve may represent source of the
epidemic
 Give information about the time course of an epidemic
and what the future course might be
 In a point-source epidemic of a known disease with a
known incubation period, epidemic curve provides
information to identify a likely period of exposure
 Shape of epidemic curve illustrates type of epidemic.


56. Mean incubation period

57. Common source single exposure:
 Sharp increase followed by a rapid decline.

58. Continuous common source outbreak:
 An abrupt increase in the number of cases but, new cases
persist for a longer time with a plateau shape instead of a
peak before decreasing.

59. • Intermittent common source:
multiple peaks

60.  Propagated source outbreak:
Number of cases
 Increase in the number of cases with progressive peaks
16
14
12
10
8
6
4
2
0
1
4
7 10 13 16 19 22 25 28 31 34
Date

61.  The spatial relationships
of cases are shown best
on a spot map.
 A spot map showing
the location of cases can
give an idea of the
source of infection like
maps show that the
cases occurred in
proximity to a body of
water, a sewage
treatment plant, or its
outflow.
DRAWING A ROUGH SPOT MAP

63.  Questions to be asked and answered:
 What is the most significant geographic distribution
of cases?
 Place of residence? Workplace?
 Do the attack rates vary by place?
 Relation to any landmark or possible source?

64. 
Usually we generate hypotheses from the beginning of
the outbreak, however, at this point, the hypotheses
are sharpened and more accurately focused.
 To consider what is known about the disease itself:
What is the agent’s usual reservoir?
B. How is it usually transmitted?
C. What vehicles are commonly implicated?
D. What are the known risk factors?
A.

65.  Talk to people who are ill: In-depth open
interviews, Group discussions
 Hypotheses should be proposed in a way that they
can be tested.

66.  After a hypothesis is formulated, one should be able to
show that:
 all additional cases, lab data, and epidemiologic
evidence are consistent with the initial hypothesis

no other hypothesis fits the data as well
 Observations that add weight to validity:
 The greater the degree of exposure (or higher dosage
of the pathogen), the higher the incidence of disease
 Higher incidence of disease in the presence of one risk
factor relative to other factors

67.  Approaches:
 Comparison of hypothesis with known/ established facts.
 Analytic epidemiology to test the hypothesis
 First method is used when the evidence is so strong
that hypothesis need not be tested

Example - A 1991 investigation of an outbreak of vitamin D
intoxication in Massachusetts.
All affected drank milk from local dairy.
Hypothesis - dairy was source, milk vehicle of excess vit D.
Visit to dairy, they quickly recognized that far more than
the recommended dose of vitamin D was inadvertently
being adding to the milk.
No further analysis was necessary.

68.  Analytic epidemiology is used when cause is less
clear.
Cohort studies
 Case control studies

 What to use?
Case
control
Rare disease/ large community
Common disease/ small community
Complete population accessible
Large amount of resources
Limited resources
Cohort
+++
-
-
+++
+/-
+++
+
++
+++
-

69. Example:
Case control study for an outbreak of Acute Gastroenteritis
following a dinner.
FOOD
ATE and ILL
N (%)
ATE and NOT ILL
N (%)
ODDS RATIO
TOMATOES
14 (82)
30 (86)
0.83
CHICKEN
13 (71)
34 (94)
0.11
ALFAALFA
SPROUTS
10 (67)
6 (17)
8.25

70.  These are additional studies undertaken to
corroborate the findings of the epidemiological
study.

Environmental studies
 Microbiological studies

Entomological studies

71.  Environmental studies often help explain why an
outbreak occurred and may be very important in
certain settings.

Example: Site of contamination of irrigation canal with
cattle urine in an outbreak of Leptospirosis in
southeastern Washington, August 1964.
Pond connected to
irrigation canal
And
Cattle around the site

72.  Microbiological studies can clinch the relationship
between suspected source and outbreak.

Example: In the above outbreak of Leptospirosis, culture
of urine from the cattle, water of the canal and blood of
affected children yielded the same strain of L. pomona.
Also, the children who had recovered showed increased
anti leptospiral antibodies.

73.  Entomological studies help identify the vector
responsible for the outbreak.

May also give useful insight into the life cycle of the
pathogen and the mode of transmission
Example:
Vector surveillance
in Chikungunya
affected villages of
Latur and Beed
districts of
Maharashtra, 2006

74.  Additional epidemiologic studies

What questions remain unanswered about the disease?

What kind of study used in a particular setting would
answer these questions?

When analytic studies do not confirm the hypotheses
 reconsider the
original hypotheses
 look for
new vehicles or modes of transmission
 Additional investigations
 Further lab studies
 Refine hypothesis till confirmation

76.  Report provides a blueprint for action.
 It also serves as a record of performance and a
document for potential legal issues.
 It serves as a reference if the health department
encounters a similar situation in the future.
 In public health literature serves the purpose of
contributing to the knowledge base of epidemiology
and public health
 Daily interim reports and final report.

77. Contents of a Report:
1. Back ground
2. Historical data
3. Methodology of investigation
4. Analysis of data (clinical data, Epidemiological
data, modes of transmission, Lab data,
Interpretation of data)
5. Control measures
6. Evaluation
7. Preventive measures

78. Report to be submitted
by investigating
officer/ team to the
next higher authority
within one week of
completion of
investigations

79.  Appropriate control measures
 based on Epidemiological, Clinical, Environmental
findings
 To prevent further spread of disease
 The elements of epidemic control include:
1. Controlling the source of the pathogen (if known)
Remove or inactivate the pathogen
2. Interrupting the transmission.
Sterilize environmental source of spread; vector control
3. Modifying the host response to exposure.
Immunization; Prophylactic chemotherapy

80.  Control measures should be implemented at
the earliest.
 DO NOT wait for laboratory confirmation to
start control measures.

81.  Follow up of outbreak
 Detect last case
 Detect and treat late complications
 Complete documentation
 Evaluation of outbreak management including
investigations (by local authorities)
Genesis of outbreak
 Early or late detection of outbreak
 Preparedness for outbreak
 Management of the outbreak
 Control measures taken and their impact


82.  Documentation and sharing the lessons learnt
Post outbreak seminar.
 Feedback to local health authorities, RRTs and other
concerned.
 Developing case studies on selected outbreaks for
training purposes.


83. Audience
Medium
Focus of the
content
Communication
objective
Epidemiologists,
laboratory
•Report
•Epidemiology
•Documentation of
the source
Public health
managers
•Summary
•Recommendations
•Action
Political leaders
•Briefing
•Control measures
•Evidence that the
situation is under
control
Community
•Press release,
interview
•Health education
•Personal steps
towards prevention
Scientific
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POSSIBLE MATRIX FOR COMMUNICATION OF
INVESTIGATION RESULTS AND FINDINGS

84.  An outbreak of fever, URI & loose motion among the
boarders of PTS, Jharoda kalan, Delhi was reported to
the MS of SJH by CDMO of SW district of Delhi on
10.07.09 .
 Cause for concern – Panic d/t novel H1N1 cases in Delhi
 RRT composition –
Epidemiologist, Physician, Microbiologist and other
doctors. (11.07.09)
 Case definition: A person with acute onset of fever with
or without sore throat, diarrhea, headache, body ache
starting from 2nd July 2009 onward.
 Line listing, Epidemiological case sheet (with travel
history), Lab analysis of samples for H1N1.

85.  Descriptive:
Time – Start = 2nd Jul, Peak = 7th Jul, Fall afterwards
 Place – Start in Tent # 40, 25 & 8; then spread. clustered
around tent no 1,9,20, 22, 27, 36 &37.
 Person – 61 cases. Mean age 22.2 yrs (20-49).

 Environmental: Crowded, ill ventilated tents. Humid
environment with low temperature.
 Lab: H1N1 negative. Influenza A +ve.
 Recommendations:



Reduce crowding, Improve ventilation
Increase staffing in dispensary and Proper record maintainance
Prompt identification and reporting of changes in disease
frequency.

86.  Outbreak of jaundice among the residents of Sector 8 of
RK Puram, New Delhi was reported to the MS of SJH by
CDMO of SW district of Delhi on 06.04.2011.
 Initial report by DSO suggested sudden onset of
jaundice.
 RRT – Epidemiologist, Physician, Microbiologist and
other personnel. To CGHS, dispensary on 06.04.2011
 Case defn : A person with signs and symptoms of
jaundice with or without elevated serum
aminotransferase levels from 1st January 2011 onwards
 Verification of outbreak by review of records of CGHS
dispensary.

87.  Rapid survey, Line listing, Spot map, Clinical
examination, Epidemiological case sheet, Blood
samples, Environmental study
 Descriptive:
Time – Rise from 15th Jan, Peak 1st week March, Decline
afterwards. Max cases in March (11/21)
 Place – Clustering around N block & adjacent to Palam rd
 Person – 15-30 yrs (50%), M > F (58.3/ 41.7)

 Lab: 3/5 recent cases +ve for Anti HEV IgM.
2/6 water samples – Fecal contamination

88.  Environmental: Water & sewer lines running
close, Intermittent water supply – Booster
pumps, Latrine near water storage tank, Sewer lines not
de-silted – overflowing, Damaged water lines. Absent
residual chlorine.
 Conclusion: Confirmed outbreak of jaundice. Lab results
 Acute Hepatitis E. Damaged water lines and
contamination from sewer lines responsible.
 Recommendations:
Proper record maintenance in CGHS dispensary(diagnosis, S/s)
 Monitoring and repairing of water lines
 Sewer lines should not be close to water supply pipeline
 Regular de-silting and cleaning of sewer line.
 Proper chlorination of water supply.


89. 1. A Dictionary of Epidemiology – 3rd ed; Last JM.
2.
3.
4.
5.
6.
2000.
Park’s Textbook of Preventive and Social Medicine
– 21st ed; Park JE. 2010.
Epidemiology – 4th ed; Gordis L. 2004.
Checklist for CRRT for outbreak investigation, NICD
2008
Oxford Textbook of Public Health – 4th ed; 2002
Mausner & Bahn Epidemiology: An Introductory
Text – 2nd ed; Mausner JS, Kramer S. 1985.

90. 7. R Bonita, R Beaglehole, T Kjellström. Basic
Epidemiology: WHO;2nd Edition.
8. Outbreak Investigations Around The World: Case
Studies in Infectious Disease Field Epidemiology;
Mark S Dworkin. 2010
9. Steps of outbreak investigation; Epidemiology in
the classroom. Excite, CDC. From www.cdc.gov
10. Raut DK, Roy N, Nair D, Sharma R. Influenza A virus
outbreak in Police Training School, Najafgarh, Delhi
– 2009. Indian J Med Res; Dec 2010; 132: 731-732

92. LARGE OUTBREAKS FROM AROUND THE WORLD –
WHO, 1999