Public Health Surveillance Objectives: After studying this lesson you will be able to: Define public health surveillance and its main components (activities)

Public Health SurveillancePublic Health Surveillance

Objectives:Objectives:After studying this lesson you will be able to:After studying this lesson you will be able to:

• • Define public health surveillance and its main Define public health surveillance and its main components (activities)components (activities)

• • List the main uses of surveillance dataList the main uses of surveillance data

• • Describe sources for data that can be used for Describe sources for data that can be used for public health surveillancepublic health surveillance

• • Describe the flow of information for reportable Describe the flow of information for reportable diseasesdiseases

Public Health Surveillance

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.

Essential activities of surveillance1.1. Identify; define and measure the health problem of interest; Identify; define and measure the health problem of interest;

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

3.3. Analyze and interpret these dataAnalyze and interpret these data

4.4. 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 and

5.5. Monitor and periodically evaluate the usefulness and quality Monitor and periodically evaluate the usefulness and quality of surveillance to improve it for future use. of surveillance to improve it for future use.

N.BN.B

surveillance of a problem surveillance of a problem doesdoes notnot include actions to control the include actions to control the problem.problem.

Surveillance is

Information for Action

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)

The components of surveillance and resulting public health action

8/4/1428 Dr. Salwa Tayel 9

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

Purposes of Public Health Surveillance

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.

Uses of Public Health SurveillanceUses of Public Health Surveillance

Assess and monitor public health Assess and monitor public health problemsproblems

Estimate magnitude of the problemEstimate magnitude of the problem Useful in setting priorities to facilitate planningUseful in setting priorities to facilitate planning 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

YearYear

Rep

ort

ed

Cases

(Th

ou

san

ds)

Rep

ort

ed

Cases

(Th

ou

san

ds)

Vaccine licensedVaccine licensed

00

5050

100

100

150

150

200

200

250

250

300

300

350350

400

400

450

450

500

500

1963

1963

1968

1968

1973

1973

1978

1978

1983

1983

1988

1988

1993

1993

1998

1998

MEASLES — by year, United States, 1983–1998MEASLES — by year, United States, 1983–1998

00

55

1010

1515

2020

2525

3030

YearYear

19831983 19881988 19931993 19981998Rep

ort

ed

Cases

(Th

ou

san

ds)

Rep

ort

ed

Cases

(Th

ou

san

ds)

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

20

10


Identifying Health Problems for Surveillance

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


Criteria for selecting and prioritizing Criteria for selecting and prioritizing health problems for surveillancehealth problems for surveillance::

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


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

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

Capacity of health system to implement controlCapacity of health system to implement control measures for the health problem:measures for the health problem:

• Immediate responseImmediate response• availability of resourcesavailability of resources

Criteria for selecting and prioritizing Criteria for selecting and prioritizing health problems for surveillancehealth problems for surveillance::


Sources and Methods for Gathering Data

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


Methods used to collect the health-related data

1. Environmental monitoring

2. Surveys

3. Notifications

4. Registries.


Surveys

• Surveys, uses a “structured and systematic

gathering of information” from a sample of “a

population of interest to describe the

population in quantitative terms.”


Notification

• 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.


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

Surveillance data usually collected are:Surveillance data usually collected are:

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

Morbidity data; infections diseases, non-

communicable diseases, birth defects, injuries,...

Mortality data

Analyzing and Interpreting Data

Analyzing by time

Analyzing by place

Analyzing by person

Interpreting results of analyses

Observed increases or decreases in disease Observed increases or decreases in disease

incidence or prevalence might be an artifact.incidence or prevalence might be an artifact.

Common causes of artifactual (not true) change in Common causes of artifactual (not true) change in

disease occurrence are:disease occurrence are:

• 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.

Disseminating Data and Interpretations

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.


Types of Surveillance1.1. 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 typical health Good for monitoring large numbers of typical health

eventsevents

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


Types of SurveillanceTypes of Surveillance2-Active (Sentinel reporting system):2-Active (Sentinel reporting system):

Collection of data on a specific disease for a relatively Collection of data on a specific disease for a relatively limited period of time.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 practice. Active surveillance is relatively expensive practice.

• It is usually limited to disease elimination programs and It is usually limited to disease elimination programs and to short-term intensive investigation and control to short-term intensive investigation and control activities, or to seasonal problems, (e.g. Influenza, activities, or to seasonal problems, (e.g. Influenza, arboviruses).arboviruses).



The End

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Public Health Surveillance Objectives: After studying this lesson you will be able to: Define public health surveillance and its main components (activities)

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