1. Public Health Surveillance
Dr Tauseef Ismail

2. Objectives After studying this lesson, you will be able to:
Define public health surveillance
List the essential activities of surveillance
Describe sources of data and data systems commonly used for public health surveillance
Analyze and interpret Surveillance data

3. The health department is responsible for protecting the public’s health, but how does it learn about cases of communicable diseases from which the public might need protection?
How might health officials track behaviors that place citizens at increased risk of heart disease or diabetes?

4. Public Health Surveillance.
The answer is
Public Health Surveillance.

6. practice

9. Some Uses of Public Health Surveillance

13. Passive:
Health-care providers send reports to a health department on the basis of a known set of rules and regulations.
Active:
Health department staff may contact healthcare providers to solicit reports.

15. A sentinel surveillance system is used when high-quality data are needed about a particular disease that cannot be obtained through a passive system.
For example, a network of large hospitals might be used to collect high-quality data on various diseases and their causative organisms, such as invasive bacterial disease caused by Hib, meningococcus or pneumococcus.
Data collected in a well-designed sentinel system can be used to signal trends, identify outbreaks and monitor the burden of disease in a community.

16. Because sentinel surveillance is conducted only in selected locations, however, it may not be as effective for detecting rare diseases or diseases that occur outside the catchment areas of the sentinel sites.
The following criteria should be considered in selecting a sentinel health facility (usually a general or infectious disease hospital) :
It should be willing to participate.
It serves a relatively large population that has easy access to it.
It has medical staff sufficiently specialized to diagnose, treat and report cases of the disease under surveillance.
It has a high-quality diagnostic laboratory.

17. This figure is an example of data gathered by sentinel sites in Afghanistan:
From this figure, we can see that measles cases were distributed throughout Afghanistan in 2001.

18. Signs and symptoms are grouped into syndrome categories
A syndrome is a constellation of signs and symptoms.
Signs and symptoms are grouped into syndrome categories
(e.g., the category of “respiratory” includes cough, shortness of breath, difficulty breathing, and so forth).
An example of syndromic surveillance is surveillance for acute flaccid paralysis (syndrome) in order to capture possible cases of poliomyelitis.

21. Reported Cases of Measles by Year, United States, 1963–1998

22. Data Tabulation by Place

23. Laboratory-confirmed West Nile Virus Human Cases, August–September, 1999

24. Incidence of Hepatitis A United States, 1998

26. Pertussis by Age Group, United States,1998

28. Analysis of Surveillance Data
Descriptive – most common
Counts, rates, ratios, proportions
Incidence, prevalence
Comparisons, means, medians, averages etc, etc, etc…….

30. What Can Account for an Apparent Increase in Cases
Change in reporting procedures/change in surveillance system
Change in case definition
Improvements in diagnostic procedures
Increased awareness
Increase access to healthcare
New physician, ICN (infection control nurse) or clinic, may see more referred cases, may make diagnosis more often or report more consistently
Laboratory or diagnostic error
Change in denominators
True increase in incidence

32. The Morbidity and Mortality Weekly Report (MMWR) Series is prepared by the Centers for Disease Control and Prevention (CDC).

37. Quiz
Which of the following statements is false? In each case, state why it is incorrect. A- During surveillance in your community, you should always collect as much information as possible, even if you do not use it. B- One of the major purposes of public health surveillance is to detect an epidemic before it can spread very far. C- A good surveillance system uses passive and active surveillance methods to collect and report the most complete data. D- Regular recording and reporting of public health data is not essential in a high quality surveillance system. E- Active surveillance covers many more diseases compared to passive surveillance.

38. ANSWERS
A is false. You should only collect data which is useful for the control of communicable diseases. B is true. Detection of an epidemic is one of the major purposes of surveillance. Surveillance can also be used to assess the magnitude of health problems, to allocate resources based on disease burdens and to evaluate progress of activities by the health facilities. C is true. A combination of active and passive surveillance is one of the indicators of a high quality surveillance system. D is false. Regular recording and reporting is one of the essential elements of a surveillance system. Without proper recording and reporting, action against communicable diseases cannot be taken. E is false. Active surveillance covers specific diseases (not all diseases), unlike a passive surveillance system.

39. A is false. You should only collect data which is useful for the control of communicable diseases.
B is true. Detection of an epidemic is one of the major purposes of surveillance. Surveillance can also be used to assess the magnitude of health problems, to allocate resources based on disease burdens and to evaluate progress of activities by the health facilities.
C is true. A combination of active and passive surveillance is one of the indicators of a high quality surveillance system.
D is false. Regular recording and reporting is one of the essential elements of a surveillance system. Without proper recording and reporting, action against communicable diseases cannot be taken.
E is false. Active surveillance covers specific diseases (not all diseases), unlike a passive surveillance system.

40. References