Progress toward containment of poliovirus Type 2 — worldwide, 2017

The Global Polio Eradication Initiative (GPEI) continues to make progress toward the eradication target. Only one of the three serotypes, wild poliovirus (WPV) type 1 (WPV1), is still circulating, and the numbers of cases and countries with endemic transmission are at record lows. With the certification of wild poliovirus type 2 (WPV2) eradication in 2015 and the global replacement of trivalent oral poliovirus vaccine (tOPV) containing Sabin poliovirus types 1, 2, and 3 with bivalent OPV containing only Sabin poliovirus types 1 and 3 during April–May 2016, poliovirus type 2 (PV2) is now an eradicated pathogen. However, in eight countries (Cameroon, Chad, Democratic Republic of Congo, Mozambique, Niger, Nigeria, Pakistan, and Syria), monovalent type 2 OPV (mOPV2) was authorized for large-scale outbreak control after tOPV withdrawal (1). Poliovirus containment, an evolving area of work that affects every country, aims to ensure that all PV2 specimens are safely contained to minimize the risk for reintroducing the virus into communities. This report summarizes the current status of poliovirus containment and progress since the last report (2), and outlines remaining challenges. Within 30 countries, 86 facilities have been designated by the relevant national authorities (usually the Ministry of Health) to become poliovirus-essential facilities for the continued storage or handling of PV2 materials; each country is responsible for ensuring that these facilities meet all biorisk management requirements. The Polio Eradication and Endgame Strategic Plan 2013–2018 (Endgame Plan) (3) of GPEI addresses four objectives: 1) poliovirus detection and interruption; 2) immunization systems strengthening and OPV withdrawal; 3) containment and certification; and 4) transition planning (previously referred to as legacy planning). Under objective 2, the Endgame Plan outlines the readiness criteria and the trigger point for initiating the phased withdrawal of vaccine viruses, starting with Sabin poliovirus type 2. The certification of eradication of WPV2 in 2015 activated the implementation of the containment work. Indigenous WPV2 was last detected in 1999; it was certified as eradicated in September 2015 by the Global Commission for the Certification of the Eradication of Poliomyelitis (GCC). WPV type 3 (WPV3) was last detected in November 2012 in Nigeria. WPV1 is the only serotype that is endemic and that is in parts only of three countries (Afghanistan, Nigeria, and Pakistan). Four World Health Organization (WHO) regions (Americas, Europe, South-East Asia, and Western Pacific) are certified as polio-free by their respective Regional Certification Commissions (RCCs). Globally, reported WPV1 cases decreased from 74 in 2015 to 37 in 2016; in 2017, six WPV1 cases were reported as of mid-June (4).