Surveillance to Track Progress Toward Polio Eradication — Worldwide, 2020–2021
Amanda L. Wilkinson, Ousmane M. Diop, Jaume Jorba, Tracie J. Gardner, Cynthia J. Snider, Jamal Ahmed
Abstract
Since the Global Polio Eradication Initiative (GPEI) was established in 1988, the number of reported poliomyelitis cases worldwide has declined by approximately 99.99%. By the end of 2021, wild poliovirus (WPV) remained endemic in only two countries (Pakistan and Afghanistan). However, a WPV type 1 (WPV1) case with paralysis onset in 2021, was reported by Malawi a year after the World Health Organization (WHO) African Region (AFR) was certified as WPV-free and circulating vaccine-derived poliovirus (cVDPV) cases were reported from 31 countries during 2020-2021 (1,2). cVDPVs are oral poliovirus vaccine-derived viruses that can emerge after prolonged circulation in populations with low immunity and cause paralysis. The primary means of detecting poliovirus transmission is through surveillance for acute flaccid paralysis (AFP) among persons aged <15 years, with confirmation through stool specimen testing by WHO-accredited laboratories, supplemented by systematic sampling of sewage and testing for the presence of poliovirus (environmental surveillance). The COVID-19 pandemic caused disruptions in polio vaccination and surveillance activities across WHO regions in 2020; during January-September 2020, the number of reported cases of AFP declined and the interval between stool collection and receipt by laboratories increased compared with the same period in 2019 (3). This report summarizes surveillance performance indicators for 2020 and 2021 in 43 priority countries* and updates previous reports (4). In 2021, a total of 32 (74%) priority countries met * Countries selected for this 2020-2021 report were identified as priority countries in the WHO Global Polio Surveillance Action Plan (GPSAP), 2022-2024 because of persistent surveillance gaps and susceptibility to poliovirus transmission or had 1 WPV1 or cVDPV isolates detected from AFP or environmental surveillance in 2021 (https://polioeradication.org/wpcontent/uploads/2022/03/GPSAP_2022-2024.pdf ). Note: In 2022, VDPV3 was isolated from an AFP case and genetically linked to VDPV3 strains isolated from environmental samples collected in Israel and the Palestinian Territories in 2021-2022 (https://www.euro.who.int/en/countries/israel/news/ news/2022/3/circulating-vaccine-derived-poliovirus-confirmed-in-israel); the emergence was confirmed as cVDPV3 in March 2022; surveillance performance in these geographies are not included in this report.