Nigeria is the last country in Africa to have witnessed a case of polio - in Borno state, in the north-east. Outside of Nigeria, the last case on the continent was in the Puntland region of Somalia, in 2014. //

But "to end polio, at least 95% of children must be vaccinated, no matter where they live," says WHO head of polio eradication Michel Zaffran. Today, only two countries - Afghanistan and Pakistan - remain polio-endemic, down from more than 125 in 1988