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Disease surveillance and notifiable diseases
Surveillance is the ongoing, systematic collection, analysis and interpretation of health data for action – and it always sees only the tip of the pyramid: few of those infected seek care, are tested, diagnosed and reported.
Why it matters in the exam
Items on this topic ask what the surveillance pyramid is and what it means (under-reporting, so the data mainly represent severe cases), how passive, active, sentinel and syndromic surveillance differ, and which diseases must be notified under the Public Health Ordinance of 1940. In Israel the treating physician and the laboratory must report to the district health office, and some diseases require immediate telephone notification already on suspicion. Also tested is polio surveillance in Israel, which includes surveillance of acute flaccid paralysis (AFP) in children and environmental sewage surveillance, and influenza surveillance through sentinel clinics. Advanced items ask about the attributes by which a surveillance system is evaluated – sensitivity, positive predictive value, timeliness, representativeness, simplicity, flexibility and acceptability – and about the difference between individual notification and aggregate reporting. Remember that a sudden rise in reports may result from awareness, a new test or a changed case definition, and not necessarily from a true rise in disease. In practice, a physician who diagnoses a listed disease does not stop at a note in the file: he completes a notification, provides identifying details and an address so the office can trace contacts, and cooperates with the epidemiological investigation. The duty to report overrides medical confidentiality, and the information is used only for public-health purposes.
Key points
- Surveillance is systematic collection, analysis and interpretation for action.
- The surveillance pyramid explains under-reporting.
- In Israel notification goes to the district health office under the Public Health Ordinance of 1940.
- Polio surveillance includes acute flaccid paralysis and sewage surveillance.
- A surveillance system is evaluated by sensitivity, predictive value, timeliness, representativeness, simplicity and acceptability.
Summary table
| Type of surveillance | How it works | Strength | Weakness |
|---|---|---|---|
| Passive | Physicians and laboratories report as required | Cheap and broad | Under-reporting and delays |
| Active | Public-health staff contact sources and search for cases | More complete and accurate | Costly; used in outbreaks or elimination |
| Sentinel | Selected clinics or laboratories report intensively | Quality data and trends | Does not count all cases |
| Syndromic | Tracks symptoms, visits and drug sales before diagnosis | Early warning | Less specific |
| Environmental and sewage | Sewage samples for viruses | Detects silent spread of polio | Does not identify individual patients |
| Laboratory-based | Positive results are sent directly | Reliable and specific | Sees only those who were tested |
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Sources
- CDC, Updated Guidelines for Evaluating Public Health Surveillance Systems, 2001 — MMWR Recommendations and Reports – system attributes
- Israel, Public Health Ordinance (פקודת בריאות העם), 1940, as amended — Notification of infectious diseases
- WHO, Communicable disease surveillance and response systems: guide to monitoring and evaluating, 2006 — Core and support functions
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.