Global polio eradication efforts have reduced WPV1 cases by 41% from 2016 to 2017, though transmission continues in Afghanistan, Pakistan, and potentially Nigeria.
In 1988, when an estimated 350,000 cases of poliomyelitis occurred in 125 countries, the World Health Assembly resolved to eradicate polio globally. Transmission of wild poliovirus (WPV) continues uninterrupted in only three countries (Afghanistan, Nigeria, and Pakistan) (1), and among the three serotypes, WPV type 1 (WPV1) remains the only confirmed circulating type. This report describes global progress toward polio eradication during January 2016-March 2018, and updates previous reports (2). In 2017, 22 WPV1 cases were reported, a 41% decrease from the 37 WPV1 cases reported in 2016. As of April 24, 2018, eight WPV1 cases have been reported (seven in Afghanistan and one in Pakistan), compared with five cases during the same period in 2017. In Pakistan, continuing WPV1 transmission has been confirmed in multiple areas in 2018 by isolation from wastewater samples. In Nigeria, ongoing endemic WPV1 transmission was confirmed in 2016 (3); although WPV was not detected in 2017 or in 2018 to date, limitations in access for vaccination and surveillance in insurgent-held areas in northeastern Nigeria might permit continued undetected poliovirus transmission. Substantial progress toward polio eradication has continued in recent years; however, interruption of WPV transmission will require overcoming remaining challenges to reaching and vaccinating every missed child. Until poliovirus eradication is achieved, all countries must remain vigilant by maintaining high population immunity and sensitive poliovirus surveillance.
Khan et al. (2018) studied this question.