Progress of polio eradication and containment requirements after eradication.

Wild poliovirus (WPV) is nearing eradication, and only three countries have never interrupted WPV transmission (Pakistan, Afghanistan, and Nigeria). WPV2 was last detected in 1999, and it was declared eradicated in 2015. WPV3 has not been detected since 2012. Since 2016, WPV1 has been detected in only two countries (Afghanistan and Pakistan), with only 22 cases reported in 2017 and 12 cases reported in 2018 (as of July 10). Because of WPV2 eradication and the risk of emergence of type 2 vaccine-derived polioviruses from continued use of trivalent oral polio vaccine (OPV), trivalent OPV was replaced by bivalent OPV (types 1 and 3) in a globally coordinated effort in 2016. WPV2 eradication and trivalent OPV cessation also mean that breach of containment in a facility working with type 2 poliovirus is now a major risk to reseed type 2 circulation in the community. As a result, the World Health Organization has developed a "Global Action Plan to minimize poliovirus facility-associated risk after type-specific eradication of wild polioviruses and sequential cessation of oral polio vaccine use." Because poliovirus has long been used as a standard for qualification of intravenous immunoglobulin, disinfectant products, and sanitation methods, poliovirus containment has implications far beyond poliovirus laboratories.