Wild poliovirus (WPV) refers to naturally occurring poliovirus strains, primarily type 1 (WPV1), as types 2 (WPV2) and 3 (WPV3) have been eradicated globally. WPV is considered endemic in only two countries, with additional countries reporting imported cases or environmental detections.
No additional countries reported WPV1 cases in 2025 beyond Pakistan and Afghanistan. However, historical importations have occurred in neighboring regions due to population movement (WHO, 2024).
Note: Malawi and Mozambique reported WPV1 cases in 2022, linked to Pakistan, but no cases have been reported since 2022 (GPEI, 2024).
Total Countries with WPV (Any Type): 2 (Pakistan, Afghanistan).
Context: WPV2 was globally eradicated in 1999, and WPV3 in 2019, leaving WPV1 as the only remaining wild strain (WHO, 2015, 2019). Pakistan and Afghanistan are the last endemic countries for WPV1, with challenges including security issues, vaccine hesitancy, and cross-border transmission (Washington Post, January 29, 2025; DW, January 24, 2025).
Circulating vaccine-derived poliovirus (cVDPV) emerges in under-immunized populations when the weakened virus in the oral polio vaccine (OPV) mutates and regains neurovirulence. cVDPV2 is the most prevalent type, but cVDPV1 and cVDPV3 also occur.
No countries reported cVDPV3 cases during this period (CDC, October 17, 2024).
Total Countries with cVDPV (Any Type): 39 (38 with cVDPV2, 3 with cVDPV1, with overlap in Democratic Republic of the Congo, Madagascar, and Mozambique).
Context: cVDPV2 is the most prevalent type, with 70 outbreaks in 38 countries during January 2023–June 2024 (CDC, October 17, 2024). cVDPV emerges in under-immunized populations, and mitigation efforts include the novel oral polio vaccine type 2 (nOPV2) and inactivated polio vaccine (IPV) (WHO, 2024).
Total Countries with Vaccine-Derived Poliovirus (cVDPV, Any Type): 39
Total Countries with Wild Poliovirus (WPV, Any Type): 2
Difference: 39 (cVDPV) - 2 (WPV) = 37 more countries have cVDPV compared to WPV.
