Polio in Nigeria
17 July 2009 - In 2009, the northern states of Nigeria have experienced a large polio outbreak due to wild poliovirus type 3 (WPV3) with 258 cases, compared to 32 cases for the same period in 2008. WPV3 from northern Nigeria has this year spread internationally to Niger. Since February 2009, there has also been an increasing number of polio cases due to a type 2 circulating vaccine-derived poliovirus (cVDPV2) in northern Nigeria (103 cases to date in 2009 compared to 31 cases for the same period in 2008). Both serotypes are at continued, and in the case of the cVDPV2 increasing, risk of international spread. While the number of cVDPV2 cases is lower than WPV3 cases, circulation of this serotype is of particular international concern as the last case of polio due to a circulating wild poliovirus type 2 (WPV2) was in 1999.
In response to these risks, Nigeria has conducted nationwide polio supplementary immunization activities (SIAs) with monovalent OPV type 3 (mOPV3) in late January 2009 and with trivalent OPV from 30 May to 2 June. Additional SIAs are planned for later in the year, including an SIA with trivalent OPV for August.
To minimize the risk and consequences of international spread of these polioviruses, countries across west and central Africa, particularly those bordering the affected states of northern Nigeria, should enhance surveillance for acute flaccid paralysis (AFP), identify subnational population immunity gaps, and strengthen routine immunization with trivalent OPV. Countries affected by poliovirus importations should continue to supplement routine immunization with large-scale outbreak response activities with the relevant OPV, as per the WHA Resolution WHA59.1.