Surveillance: An Overview

Surveillance: An Overview

Prof Ahmed Mandil

KSU College of Medicine

Headlines

• Public health approach

• Definitions

• Components of a Surveillance System

• Reporting and Feedback

• Steps of Surveillance

• Uses of Surveillance Data

• Examples of Surveillance Activities

April 21, 2023 2Surveillance

April 21, 2023 Surveillance

Public Health Approach

Problem Response

Surveillance:What is the

problem?

Risk FactorIdentification:What is the

cause?

InterventionEvaluation:

Whatworks?

Implementation:How do you

do it?

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Definitions (I)

• Register: a list of persons or disease cases in a community, organization or group of people which does not have a control component (as in a surveillance system). An example is cancer registers such as the National Cancer Registry in Riyadh

• Monitoring system: a general term describing a system for watching or checking on a person or thing

• Surveillance of disease: continuous scrutiny of all aspects of occurrence and spread of disease that are pertinent to effective control

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Definitions (III)

• Surveillance of persons: continuous scrutiny of disease contacts or high risk groups in order to promote recognition of infection or illness

• Sentinel event: "a preventable disease / disability/death whose occurrence serves as a warning that prevention may need to be improved". Sentinel surveillance represents a wide range of activities that focus on key health indicators in the population.



Surveillance: Comprehensive Definition

Ongoing, systematic collection, analysis, and interpretation of data essential to planning, implementation, and evaluation of interventions, closely integrated with the timely dissemination of these data to other stake holders (e.g. health professionals, public officials, international agencies, general public)

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Components (I): Introduction

A surveillance system is a monitoring process with a control system. The key words in such a system are: registration and monitoring of disease occurrence. It simulates a thermostat in a home with central heat and air-conditioning. Inhabitants of the home set the desired (comfortable) temperature on a thermostat. The thermostat 's thermometer "senses" temperature. It then compares the "actual" with "desired" temperature. It sends "control signals" to the heater or the air conditioner: if the temperature is too high, the air-conditioner goes on; conversely, if the temperature is too low, the heat goes on.


Components (II)

Similarly, the components of a surveillance are:

• Sensor: identifies the state of health. Examples are: local physicians (for notifiable diseases), health workers, labs (for routine sampling, e.g. for genetic disorders), teachers & school nurses (for disease-related absenteeism), industrial physicians, or annual examination of the military

• Reference Signal: the output of the sensor


Components (III)

• Monitor & Expectations: compares the reference signal with "expectations". This is usually an epidemiologist, who compares the disease occurrence with a prior expectation (threshold of concern) and responds accordingly.

• Error Signal: output of the monitor which measures difference between performance (reference signal) and expectation. Example: morbidity & mortality weekly reports.

• Controller: person or organization that takes corrective action aimed at reducing the error signal, i.e. initiates prevention and control activities. This might be the local health officer (regionally), or the chief medical officer (e.g. minister of health) if a national decision is needed.



Controller(Decision maker) Monitor

SensorSensor((ReportersReporters))

Expectations

Error Signal(Monitor output)

Reference Signal (Sensor output)

COMPONENTS OF COMPONENTS OF A SURVEILLANCE SYSTEMA SURVEILLANCE SYSTEM

COMPONENTS OF COMPONENTS OF A SURVEILLANCE SYSTEMA SURVEILLANCE SYSTEM

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Feedback & Reporting

• Passive reporting: mailing printed forms by physicians and nurses of all cases of reportable diseases observed in previous week, or telephone reporting in other cases.

• Active Reporting: ministry of health contacts physicians and nurses at periodic intervals requesting data on specific diseases. (not as common as passive reporting)



Steps for Surveillance

• Defining the problem• Collecting data• Entering / processing data• Interpreting data• Reporting results• Using results to plan interventions• Evaluating the surveillance system• Updating the system

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Surveillance Sources(Communicable Diseases)

• Morbidity and mortality reports; • Reports of field investigations of epidemics and

individual cases • Lab isolation and identification of infectious

agents • Data concerning vaccines, toxoid, immune

globulins, and insecticides

• Immunity levels in segments of the population.


.Surveillance Sources

(Non-Communicable Diseases)

• Notifiable diseases: lead poisoning reporting systems

• Vital statistics (death certificates)• Sentinel surveillance (SENSOR): for occupational

risks• Disease registries: cancer, ARF/RHD registries• Health surveys: behavioral risk factor telephone

surveys• Census data: poverty rates by district/region/city


Uses of Surveillance • Estimate magnitude of the problem• Portray the natural history of a disease• Determine distribution and spread of illness• Detect outbreaks• Generate hypotheses, stimulate research• Evaluate control and prevention measures• Monitor changes in infectious agents• Detect changes in health practices• Facilitate planning


Uses of Public Health Surveillance

• Estimate magnitude of the problem

• Portray the natural history of a disease

• Determine distribution and spread of illness

• Detect outbreaks

• Generate hypotheses, stimulate research

• Evaluate control measures

• Monitor changes in infectious agents

• Detect changes in health practices

• Facilitate planning


Shigellosis

1968-1998

00

55

1010

1515

YearYear

1968

1968

1973

1973

1978

1978

1983

1983

1988

1988

1993

1993

1998

1998

Rep

ort

ed

cases p

er

100,0

00

pop

ula

tion

Rep

ort

ed

cases p

er

100,0

00

pop

ula

tion

Source: CDC. Summary of notifiable diseases. 1998.

TOXIC SHOCK SYNDROME (TSS)United States, 1983-1998


*Includes cases meeting the CDC definition for confirmed and probable cases for staphylococcal TSS.

1983 1984 1985 1986 1987 1988 19891990 1991 1992 1993 1994 1995 1996 1997 1998

National Center for Infectious Diseases (NCID) data*

National Electronic Telecommunications System for Surveillance (NETSS) data

0

20

40

60

80

100

120

140

160

Year (Quarter)

Rep

ort

ed

cases



• Estimate magnitude of the problem• Portray the natural history of a disease• Determine distribution and spread of

illness• Detect outbreaks• Generate hypotheses, stimulate research• Evaluate control measures• Monitor changes in infectious agents• Detect changes in health practices• Facilitate planningApril 21, 2023 20Surveillance



*Includes cases meeting the CDC definition for confirmed and probable cases for staphylococcal TSS.

1983 1984 1985 1986 1987 1988 19891990 1991 1992 1993 1994 1995 1996 1997 1998

National Center for Infectious Diseases (NCID) data*

National Electronic Telecommunications System for Surveillance (NETSS) data

0

20

40

60

80

100

120

140

160

Year (Quarter)

Rep

ort

ed

cases


Botulism (Foodborne) United States, 1978-1998

*Data from survey of state epidemiologists and directors of state public health laboratories. Not yet available for 1998.

*Data from survey of state epidemiologists and directors of state public health laboratories. Not yet available for 1998.

Outbreak caused by potato salad, NM

Outbreak caused by potato salad, NM

Outbreak caused by sautéed onions, IL

Outbreak caused by sautéed onions, IL

Outbreak caused by fermented fish/sea products, AK

Outbreak caused by fermented fish/sea products, AK

Outbreak caused bybaked potatoes, TX

Outbreak caused bybaked potatoes, TX

Laboratory-confirmed cases*Laboratory-confirmed cases*NETSS dataNETSS data

00

1010

2020

3030

4040

5050

6060

7070

8080

9090

100100

110110

YearYear19781978 19831983 19881988 19931993 19981998

Rep

ort

ed

cases

Rep

ort

ed

cases

Source: CDC. Summary of notifiable diseases. 1998.

Examples (I)

• For diseases:

– Communicable diseases: influenza, HIV/AIDS, sexually-transmitted infections

– For disease outbreaks: e.g. food poisoning, salmonelosis, cholera

– Non-communicable diseases: lead poisoning, cancer, hypertension, diabetes

– Risk factors: tobacco use, physical exercise


Examples (II)

• For emergencies: bioterrorism, chemical, radiation, natural disasters

• For hospitals: e.g. nosocomial infections.

• In the industry: for occupational disorders.

• In the military: for diseases of the recruits


References

• Teutsch SM, Churchill RE. Principles and practice of public health surveillance. Oxford: Oxford university press, 2000

• Surveillance of communicable disease surveillance:

http://www.cdc.gov/idsr/resources.htm

• Surveillance of emergencies: http://emergency.cdc.gov/episurv/

• Surveillance of non-communicable disease risk factors: http://www.who.int/mediacentre/factsheets/fs273/en/


Surveillance: An Overview

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