This document discusses disease surveillance methods. It defines surveillance as the systematic collection and analysis of health data to guide disease control activities. Surveillance can be either passive, relying on routine reporting from healthcare providers, or active, involving direct identification of cases. Both methods have advantages and limitations. The document reviews reasons for conducting surveillance like detecting outbreaks and evaluating health programs. It also provides examples of how to analyze surveillance data by person, place, and time to identify trends and target public health efforts.
2. Surveillance
• For persons who need to carry out surveillance activities
but have little prior experience or training
• Also helpful for people who would like to better
understand the process and reasoning behind
surveillance methods and interpretation
3. SURVEILLANCE
• Surveillance is data collection for action.
• The mere collection and compilation of disease-
related data without analysing them and taking
appropriate action is not surveillance.
• Disease surveillance is the systematic collection, analysis
and dissemination of data on diseases of public health
importance so that appropriate action can be taken to
either prevent or stop further spread of disease.
• It guides disease control activities and measures the
impact of immunization services.
4. What Is Surveillance?
• Centers for Disease Control and Prevention (CDC):
surveillance is “ongoing systematic collection, analysis,
and interpretation of health data essential to the
planning, implementation, and evaluation of public
health practice, closely integrated with the timely
dissemination of these data to those who need to know.”
5. Examples of surveillance
• Communicable diseases
• Health behaviors:
• Drug use, risky sexual behavior
• Risk factors for chronic diseases (e.g. smoking)
• Environmental risks and diseases
• Health care
6. WHY IS DISEASE SURVEILLANCCE
NECESSARY ?
Disease surveillance is used to
• predict or detect disease outbreaks with a view to
investigation and containment
• Identify high risk population and areas requiring special
attention.
• Monitor impact and progress towards disease eradication ,
elimination and control
• identify areas in which system performance is poor, so that
corrective measures can be taken
7. • monitor programme effectiveness by documenting short- and
long-term effects of immunization on disease burden .
• identify circulating strains including serotype , genotypes and
subtypes .
• Determine the frequency of occurrence of a disease in a
community and the burden of disease .
8. IMPORTANCE
• Collecting data is merely one step
• Critical goal is to control and/or prevent diseases
• Any data collected must be organized and carefully
examined
• Any results need to be communicated to public health
and medical communities
9. • Vital to communicate results
• During potential outbreak so public health and medical
communities can help with disease prevention and control
efforts
• During non-outbreak times to provide information about
baseline levels of disease
• Baseline provides information to public health officials monitoring health at
community level, serves as reference in future outbreaks
10. SURVEILLANC METHODS
• Classified as
passive
active
• Passive surveillance-Regular reporting of disease data by
all institutions that see patients (or test specimens) and
are part of a reporting network.
• There is no active search for cases.
• It involves passive notification by surveillance sites and
reports are generated and sent by local staff.
11. • relies on the cooperation of health-care providers —
laboratories, hospitals, health facilities and private practitioners
— to report.
• Once the data have been received, they must be compiled and
then analysed to monitor disease patterns and identify possible
outbreaks.
• Involves the regular collection and reporting of surveillance
data and is the commonest method.
• Less expensive than other surveillance strategies and covers
wide areas (whole countries or provinces)
• However, because it relies on an extensive network of health
workers, it can be difficult to ensure completeness and
timeliness of data
12. • In Some countries might not have the capacity or resources to
identify all cases a disease, either because the diagnosis of the
disease requires specialized clinical skills or because laboratory
resources are not available throughout the country.
• Under these circumstances, passive surveillance can be
adapted in a number of ways, depending on the completeness
and quality of data required, financial constraints and the
availability of specialist skills and services.
13. • Active surveillance-involves visiting health facilities,
talking to health-care providers and reviewing medical records
to identify suspected cases of disease
• Involves physical review of medical records and registers,
interviews with health workers and visits to relevant
outpatient clinics and hospital wards under surveillance.
• When a case is found, the active surveillance staff investigate
it, document clinical and epidemiological data, arrange to
send appropriate laboratory specimens and report the
information rapidly.
• usually used when a disease is targeted for eradication or
elimination,
14. • Is more difficult to set up and expensive to conduct.
• It does not replace passive surveillance but complements
it.
• If conducted regularly it has the following advantages:
• helps to improve the timeliness and accuracy of case
detection and reporting.
• Enables rapid case investication ,including taking
laborator specimens.
• Is closely linked to the laboratory system through
individual case identification.
• Enables timely action to be taken in response to the
detected case.
15. Passive
surveillance/nationwide
routine
Active surveillance
Population under
surveillance
Whole country All cases attending selected
health facilities
Outcome
measures
Cases and death
Incidence rates
Trends in epidemiology
Cases and deaths in selected
heath facility
Full case investigation with
details on each case
Advantages Can provide accurate rates
and data on burden if
reporting
is complete and supported
by reliable laboratory
results
Directs eradication or
elimination programmes
Can be expanded to include
additional diseases as
Required.
Rapid detection of outbreaks
Disadvantages Needs extensive clinical
laboratory resources
Reporting is rarely complete
and timely
Heavy demands on data
management
Resource-intensive
Requires dedicated staff,
transport, management
Heavy demands on data
management
16. Why Is Surveillance Important?
• Surveillance information has many uses:
• Monitoring disease trends
• Describing natural history of diseases
• Identifying epidemics or new syndromes
• Monitoring changes in infectious agents
• Identifying areas for research
• Evaluating hypotheses
• Planning public health policy
• Evaluating public health policy/interventions
17. • Examples of uses of surveillance data:
• Evaluating impact of national vaccination campaigns
• Identifying AIDS when unknown syndrome
• Estimating impact of AIDS on US health care system in 1990s
(using mathematical models based on surveillance data)
• Identifying outbreaks of rubella and congenital rubella
among Amish and Mennonite communities in 6 states in
1990 and 1991 (3)
• Monitoring obesity, physical activity,other indicators for
chronic diseases
18. How to Conduct Surveillance
• Surveillance data allow description and comparison of
patterns of disease by person, place, and time
• Several ways to describe and compare patterns, from
straightforward presentations to statistically complex
analyses
• Will concentrate on simple techniques
19. How to Conduct Surveillance:
Person
• When available, demographic characteristics such as
gender, age, race/ethnicity, occupation, education level,
socio-economic status, sexual orientation, immunization
status can reveal disease trends
• Example: looking at Streptococcus pneumoniae, a
common cause of community-acquired pneumonia
and bacterial meningitis, examining distribution of cases
by race provides important information about burden of
disease in different populations
20. How to Conduct Surveillance:
Person – Numbers and Rates
• data collected on Streptococcus pneumoniae from CDC
Emerging Infections Program Network, a surveillance
program that collects data from multiple countries in US
states .
21. How to Conduct Surveillance:
Person – Numbers and Rates
• Data show majority of cases reported among whites
• Can draw only limited conclusions because race not
recorded for 684 cases (15%)
• Shows only number of reported cases, not rate
• Total number of individuals by race needed to determine
if there is a disproportionate burden of disease among
races
22. How to Conduct Surveillance: Place
• Best to characterize cases by place of exposure rather
than by place at which cases reported
• The two may differ and place of exposure is more
relevant to epidemiology of a disease
• Example: travelers on a cruise ship exposed to a disease just prior
to disembarking but become symptomatic and are diagnosed
after return to various home locations
• Example: person exposed to disease in small rural town but
referred to tertiary care center 100 miles away where disease is
diagnosed and reported
23. How to Conduct Surveillance: Place
– Presenting Data
• Data by geographic location can be presented in a table
• Also helpful to use maps to facilitate recognition of
spatial associations in data
• Inferential analysis can also be done using multilevel
modeling, other statistical methods
24. How to Conduct Surveillance: Time
• Compare number of cases reported in time period of
interest (weeks, months, years) to number of cases
reported during similar historical period
• Usually a delay (sometimes months to years) between
disease onset and date when disease is reported, so
preferable to use date of onset, if available, rather than
date of report
25. Data Presentation
• Surveillance data must be presented in way that
is easy to understand and interpret
• Many ways to display surveillance data
• Line graphs for displaying data by time
• Maps for presenting data in geographic context
• Graphical displays such as histograms, frequency
polygons, box plots, scatter diagrams, bar charts, pie
charts, or stem-and-leaf displays
• Spot or chloropleth maps
• Single/multivariable tables
26. • The choice of a particular graph or table depends on type of
data, but presentation should be simple and easy to follow
• Should provide all information necessary to interpret the
figure without referring to text
• Include concise title that describes subject or disease, time,
place (when relevant)
• Define any abbreviations or symbols
• Note any data exclusions
27. Surveillance methods:
surveys
• Examples:
• National Population Health Survey
• Sante Quebec
• Content:
• Conditions, behaviours not easy to monitor routinely
(mental health problems, smoking, use of
complementary/alternative therapies)
28. Conclusion
• Surveillance is valuable tool that can serve many
purposes
• When surveillance data is collected, analyzed,
interpreted, reported appropriately, these data can
provide important information about disease patterns to
inform public health practice and policy
