In September 2015, Nigeria, the last polio-endemic country in Africa, was declared by the WHO to be 'polio-free'. The country had not recorded a single new case of the disease in a year, fulfilling international requirements for removal from the polio-endemic list. This moment was seen as a historic public health achievement in the African context and in the global polio eradication effort.
Just a year later, however, this declaration was proven premature. At the time of the declaration, a significant part of the territory of North-East Nigeria's Borno state was controlled by the terrorist group, Boko Haram. By September 2016, however, the large majority of this territory had been reclaimed by the Nigerian government. With these military victories, though, came the end of Nigeria's polio-free status, as three cases of paralysis due to polio were found in territories previously occupied by Boko Haram. This illustrates the means through which social turmoil may contribute to viral emergence and reemergence.