Dr Khyati Boriya

After studying this lesson you will be able to:After studying this lesson you will be able to:• • Define public health surveillance and its Define public health surveillance and its

main components (activities)main components (activities)• • List the main uses of surveillance dataList the main uses of surveillance data• • Describe sources for data that can be used Describe sources for data that can be used

for public health surveillancefor public health surveillance• • Describe the flow of information for Describe the flow of information for

reportable diseasesreportable diseases

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Ongoing, systematic collection, analysis, and interpretation of health-related data essential to the planning, implementation, and evaluation of public health practice,

with the timely dissemination of these data to those responsible for prevention and control.

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1.1. Identify; define and measure the health problem of Identify; define and measure the health problem of interest; interest;

2.2. Collect and compile data about the problem (and if Collect and compile data about the problem (and if possible, factors that influence it)possible, factors that influence it)

3.3. Analyze and interpret these dataAnalyze and interpret these data4.4. Provide these data and their interpretation to those Provide these data and their interpretation to those

responsible for controlling the health problem andresponsible for controlling the health problem and5.5. Monitor and periodically evaluate the usefulness and Monitor and periodically evaluate the usefulness and

quality of surveillance to improve it for future use. quality of surveillance to improve it for future use. N.BN.Bsurveillance of a problem surveillance of a problem doesdoes notnot include actions to include actions to

control the problem.control the problem.

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Information for Action

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Summaries,Interpretations,Recommendatio

ns

Reports

HealthAgencie

s

Health Care

Providers

Public

Analysis

Information Loop of Public Health Information Loop of Public Health SurveillanceSurveillance

(involving health care providers, public health (involving health care providers, public health agencies, and the public)agencies, and the public)

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The components of surveillance and resulting public health action

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Measurement and recording

Transactional data

Data Management•Quality checks•Editing

Data preprocessing for a specific purpose

(‘views’, ‘data marts’)

Analytical applications

Interpretation for associations,trends, unusual patterns, signals

Public health responsePopulation of interest Population of interest which generates eventswhich generates events

Surveillance System Components

Public health surveillance provides Public health surveillance provides and interprets data to facilitate the and interprets data to facilitate the prevention and control of disease.prevention and control of disease.

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Assess and monitor public health problemsAssess and monitor public health problems Estimate magnitude of the problemEstimate magnitude of the problem Useful in setting priorities to facilitate Useful in setting priorities to facilitate

planningplanning Portray the natural history of a diseasePortray the natural history of a disease Detect epidemics/define a problemDetect epidemics/define a problem Generate hypotheses, stimulate researchGenerate hypotheses, stimulate research Evaluate programs, control measuresEvaluate programs, control measures Detect changes in health practices & servicesDetect changes in health practices & services

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Year

Repo

rted

Cas

es

(Tho

usan

ds)

Vaccine licensed

0

50

100

150

200

250

300

350

400

450

500

1963

1968

1973

1978

1983

1988

1993

1998

MEASLES — by year, United States, 1983–1998

0

5

10

15

20

25

30

Year1983 1988 1993 1998Re

port

ed C

ases

(T

hous

ands

)

Evaluate control measures of MEASLESEvaluate control measures of MEASLESUnited States, 1963-1998

20

10

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Selecting a Health Problem for Surveillance:

Conducting surveillance for a health problem consumes time and resources.

It is important to select and prioritizing health It is important to select and prioritizing health problems for surveillanceproblems for surveillance

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Public health importance of the Public health importance of the problem:problem:

incidence, prevalence,incidence, prevalence, severity, sequela, disabilities,severity, sequela, disabilities, mortality caused by the problem,mortality caused by the problem, socioeconomic impact,socioeconomic impact, communicability,communicability, potential for an outbreak,potential for an outbreak, public perception and concern, andpublic perception and concern, and international requirements.international requirements.

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Ability to prevent, control, or treat the Ability to prevent, control, or treat the health problem:health problem:

preventability andpreventability and Availability of control measures and treatment.Availability of control measures and treatment.

Capacity of health system to implement Capacity of health system to implement controlcontrol measures for the health problem:measures for the health problem:

Immediate responseImmediate response availability of resourcesavailability of resources

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Three main sources: Individual Persons Health-care providers, facilities, and records

— Physician offices— Hospitals— Outpatient departments— Emergency departments— Inpatient settings— Laboratories

3. Environmental conditions— Air— Water— Animal vectors

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1. Environmental monitoring2. Surveys3. Notifications4. Registries.

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Surveys, uses a “structured and systematic gathering of information” from a sample of “a population of interest to describe the population in quantitative terms.”

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A notification is the reporting of certain diseases or other health-related conditions by a specific group, as specified by law, regulation, or agreement.

Notifications are typically made to the state or local health agency.

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Reregistery Reregistery is a method for documenting or is a method for documenting or tracking events or persons over time.tracking events or persons over time.

Examples:Examples: Registries of vital events (birth and death Registries of vital events (birth and death

certificates) are required by law and contain certificates) are required by law and contain important health-related information. important health-related information.

A disease registry (e.g., a cancer registry) A disease registry (e.g., a cancer registry) tracks a person with disease over time and tracks a person with disease over time and usually includes diagnostic, treatment, and usually includes diagnostic, treatment, and outcome information.outcome information.

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Vital events, births, deaths, marriages, divorce,...

Morbidity data; infections diseases, non-communicable diseases, birth defects, injuries,...

Mortality data

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Analyzing by time Analyzing by place Analyzing by person

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Observed increases or decreases in disease Observed increases or decreases in disease incidence or prevalence might be an incidence or prevalence might be an artifact.artifact.

Common causes of artifactual (not true) Common causes of artifactual (not true) change in disease occurrence are:change in disease occurrence are:

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• Changes in local reporting procedures or policies (e.g., a Changes in local reporting procedures or policies (e.g., a change from passive to active surveillance).change from passive to active surveillance).• Changes in case definition (e.g., AIDS in 1993).Changes in case definition (e.g., AIDS in 1993).• Increased health-seeking behavior (e.g., media publicity Increased health-seeking behavior (e.g., media publicity

prompts persons with symptoms to seek medical care).prompts persons with symptoms to seek medical care).• Increase in diagnosis.Increase in diagnosis.• New laboratory test or diagnostic procedure.New laboratory test or diagnostic procedure.• Increased physician awareness of the condition, or a new Increased physician awareness of the condition, or a new

physician is in town.physician is in town.• Increase in reporting (i.e., improved awareness of Increase in reporting (i.e., improved awareness of

reporting). reporting). • Outbreak of similar disease, misdiagnosed as disease of Outbreak of similar disease, misdiagnosed as disease of

interest. interest. • Laboratory error.Laboratory error.

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Data and interpretations should be sent to:Data and interpretations should be sent to:•those who provided reports or other data (e.g., those who provided reports or other data (e.g., health-care providers and laboratory directors). health-care providers and laboratory directors).

They should also be sent to those who use them forThey should also be sent to those who use them for•planning or planning or •managing control programs, managing control programs, •Administrative purposes, Administrative purposes, •or other health-related decision-making.or other health-related decision-making.

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1.1. Passive (Routine reporting system)Passive (Routine reporting system) Hospitals, health centers, health facilities.Hospitals, health centers, health facilities.Reporting is governed by existing local rules. Reporting is governed by existing local rules. Advantages:Advantages:

Inexpensive.Inexpensive. Standardized.Standardized. Good for monitoring large numbers of Good for monitoring large numbers of

typical health eventstypical health eventsDisadvantages:Disadvantages:

Under-reporting is a problemUnder-reporting is a problem Incomplete dataIncomplete data Busy doctors & nursesBusy doctors & nurses

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2-Active (Sentinel reporting system):2-Active (Sentinel reporting system):Collection of data on a specific disease for a Collection of data on a specific disease for a

relatively limited period of time.relatively limited period of time.By selected health units, certain physicians,…By selected health units, certain physicians,…Advantages:Advantages:

More consistent pictures.More consistent pictures. Motivated.Motivated.

Disadvantages:Disadvantages: Not representativeNot representative Active surveillance is relatively expensive Active surveillance is relatively expensive

practice. practice. It is usually limited to disease elimination It is usually limited to disease elimination

programs and to short-term intensive programs and to short-term intensive investigation and control activities, or to investigation and control activities, or to seasonal problems, (e.g. Influenza, seasonal problems, (e.g. Influenza, arboviruses).arboviruses).

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