The efficiency and reliability of polio surveillance
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Updated: Oct 3, 2026
Particle Agglutination Method for Poliovirus Identification
Published on: April 20, 2011
1National Public Health Institute (KTL), Enterovirus Laboratory, Helsinki, Finland.
Insights
Acute flaccid paralysis (AFP) surveillance is key for polio eradication, but less sensitive as polio nears elimination. Environmental and enterovirus surveillance offer complementary approaches to detect poliovirus circulation.
Area of Science:
- Public Health
- Virology
- Epidemiology
Background:
- Acute flaccid paralysis (AFP) surveillance is crucial for polio eradication efforts.
- AFP surveillance sensitivity decreases as wild poliovirus (WPV) incidence approaches zero.
- Current surveillance methods face challenges in detecting low-level WPV circulation.
Purpose of the Study:
- To evaluate the effectiveness of AFP surveillance in polio eradication.
- To explore alternative and complementary surveillance strategies for poliovirus detection.
- To assess the potential of environmental and enterovirus surveillance.
Main Methods:
- Review of AFP surveillance data and its limitations.
- Analysis of the potential sensitivity of environmental surveillance under optimal conditions.
- Discussion of enterovirus surveillance in routine diagnostic services.
Main Results:
- AFP surveillance sensitivity declines significantly when true polio cases are rare.
- Environmental surveillance can be highly sensitive in detecting poliovirus, but requires optimal conditions (e.g., converging sewage systems).
- Enterovirus surveillance is feasible only in specific settings with comprehensive diagnostic coverage.
Conclusions:
- No single surveillance method guarantees 100% certainty of WPV elimination.
- Combining AFP, environmental, and enterovirus surveillance optimally can increase confidence in WPV eradication.
- Reaching a high probability of elimination allows for the safe cessation of polio immunization.
Abstract:
Surveillance for acute flaccid paralysis (AFP) in children younger than 15 years, and careful investigation of the cases, are the cornerstones for monitoring the progress of the poliomyelitis eradication programme. However, its sensitivity to detect wild type poliovirus (wtPV) circulation decreases when the incidence of true polio cases approaches zero. Under these conditions, only about one in 100,000 children is being investigated for poliovirus excretion. No real alternative approach which is generally exploitable has been developed. Environmental surveillance may in optimal conditions be at least as sensitive in detecting poliovirus circulation as AFP surveillance. However, optimal conditions, i.e. converging sewage systems, are not used by most people in the remaining endemic countries. Enterovirus surveillance, based on isolation of poliovirus in the routine diagnostic services, is only applicable in a few countries, where the diagnostic activity covers the entire population. Whichever approach is used, we will never reach 100% certainty of complete elimination of wtPV circulation. However, by applying all these approaches optimally, we may eventually reach a probability level allowing the safe cessation of immunisation.
