Download KSU Surveillance

Surveillance:
An Overview
Prof Ahmed Mandil
KSU College of Medicine
Headlines
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Public health approach
Definitions
Components of a Surveillance System
Reporting and Feedback
Steps of Surveillance
Uses of Surveillance Data
Examples of Surveillance Activities
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Public Health
Approach
Surveillance:
What
is the
problem?
Intervention
Evaluation:
What
works?
Risk Factor
Identification:
What is the
cause?
Problem
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Implementation:
How do you
do it?
Response
Surveillance
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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.
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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 airconditioning. 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.
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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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Sensor
(Reporters)
Controller
Error Signal
(Decision maker)
(Monitor output)
COMPONENTS OF
A SURVEILLANCE SYSTEM
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Surveillance
Reference Signal
(Sensor output)
Monitor
Expectations
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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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Steps for Surveillance
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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)
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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
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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
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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
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Reported cases per 100,000
population
1968-1998
10
5
0
1968
1973
1978
1983
1988
1993
Year
Source: CDC. Summary of notifiable diseases. 1998.
1998
Uses of Public Health
Surveillance
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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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TOXIC SHOCK SYNDROME (TSS)
United States, 1983-1998
16
0
National Center for Infectious Diseases (NCID) data*
National Electronic Telecommunications System for
Surveillance (NETSS) data
Reported cases
14
0
12
0
10
0
8
0
6
0
4
0
2
0
0
1983
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1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
Year (Quarter)
*Includes cases meeting the CDC definition for confirmed and probable cases for staphylococcal TSS.
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Uses of Public Health
Surveillance
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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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TOXIC SHOCK SYNDROME (TSS)
United States, 1983-1998
16
0
National Center for Infectious Diseases (NCID) data*
National Electronic Telecommunications System for
Surveillance (NETSS) data
Reported cases
14
0
12
0
10
0
8
0
6
0
4
0
2
0
0
1983
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1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
Year (Quarter)
*Includes cases meeting the CDC definition for confirmed and probable cases for staphylococcal TSS.
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Uses of Public Health
Surveillance
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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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Botulism (Foodborne)
United States, 1978-1998
110
100
Reported cases
90
80
Outbreak caused by
potato salad, NM
Outbreak caused by
sautéed onions, IL
Outbreak caused by
fermented fish/sea
products, AK
70
Laboratory-confirmed
cases*
NETSS data
Outbreak caused by
baked potatoes, TX
60
50
40
30
20
10
0
1978
1983
1988
1993
Year
1998
Source: CDC. Summary of notifiable diseases. 1998.
*Data from survey of state epidemiologists and directors of state public health laboratories.
Not yet available for 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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