Surveillance to track progress towards poliomyelitis eradication -- worldwide, 2022--2023.

The reliable and timely detection of poliovirus infection through surveillance for acute flaccid paralysis (AFP), supplemented by environmental surveillance (ES) of sewage samples,is a critical component of the polio eradication programme. Since 1988, the number of polio cases caused by wild poliovirus (WPV) has decreased by >99.9%, and eradication of WPV serotypes 2 and 3 has been certified; only serotype 1 (WPV1) continues to circulate and transmission remains endemic in Afghanistan and Pakistan. In this surveillance update, we evaluated indicators of AFP in surveillance, ES for polioviruses and data on the performance of the Global Polio Laboratory Network (GPLN) provided by 28 priority countries for the programme during 2022--2023. No WPV1 cases have been detected outside those countries since August 2022, when importation into Malawi and Mozambique resulted in an outbreak during 2021--2022. During 2022--2023, 20 of 28 priority countries (71.4%) met national AFP surveillance indicator targets, and the number of ES sites increased. Low national rates of reported AFP cases in priority countries in 2023 might have been due to lags in surveillance reporting; substantial national and subnational AFP surveillance gaps persist. Maintaining high-quality surveillance is critical to achieving the goal of global polio eradication. Monitoring surveillance indicators is important to identifying gaps and guiding surveillance-strengthening activities, particularly in countries at high risk for poliovirus circulation. [ABSTRACT FROM AUTHOR]