Number of confirmed cases of poliomyelitis
Rationale for use
The 1988 World Health Assembly (WHA) called for the global eradication of poliomyelitis. The number of poliomyelitis cases is used to monitor progress towards this goal and to inform eradication strategies. Countries implement strategies supplementing routine immunization - e.g. national immunization days and sub-national campaigns - or more targeted mop-up activities, depending on the levels of poliomyelitis cases.
Definition
Suspected polio cases (acute-flaccid paralysis - AFP, other paralytic diseases, and contacts with polio cases) that are confirmed by laboratory examination or are consistent with polio infection.
Data sources
Active case finding and reporting of AFP, communicable disease surveillance systems, national and regional laboratory reports*.
* Most countries conduct active case search for cases of acute flaccid paralysis among children less than 15 years of age. When possible (approximately 80% of cases) a stool specimen is obtained for laboratory investigation. A regional reference laboratory verifies cases with evidence of polio infection. The principle indicator for the quality of AFP/polio surveillance data is the use of the non-polio AFP rate. Studies have shown that the expected non-polio AFP rate is approximately 1 per 100 000 population under 15 years of age and an effective polio surveillance system should detect and report approximately one AFP case per 100 000 population under 15.
Methods of estimation
Estimates of polio cases are based exclusively on unadjusted surveillance data.
Disaggregation
By location (urban/rural, major regions/provinces).
References
Database
- Information on Vaccines, Immunization and Biologicals
- WHO Vaccines preventable diseases monitoring system
Comments
Many countries have eliminated indigenous polio and in some instances more than ten years have passed since the last reported case of polio. Intensive, high quality surveillance is difficult to maintain when effective interventions have eliminated the disease locally.