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?
3
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.
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April 21, 2023 Surveillance
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)
6
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.
April 21, 2023 Surveillance 7
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
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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.
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April 21, 2023 Surveillance
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)
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April 21, 2023 Surveillance
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.
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.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
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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
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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
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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.
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
April 21, 2023 18Surveillance
TOXIC SHOCK SYNDROME (TSS)United States, 1983-1998
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
April 21, 2023 19Surveillance
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 planningApril 21, 2023 20Surveillance
TOXIC SHOCK SYNDROME (TSS)United States, 1983-1998
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
April 21, 2023 21Surveillance
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
April 21, 2023 22Surveillance
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
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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
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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/
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