Polio has nearly been eradicated from Africa. It might soon be active in only 2 countries worldwide.

The last time a child was paralyzed from polio in Nigeria was July 24, 2014. Now the World Health Organization is saying that if no new cases arise by July 24, 2015, it will consider Nigeria off the list of countries with active transmission, leaving only two left in the world: Pakistan and Afghanistan.

The disease's last foothold on the African continent, Nigeria has long struggled to be polio-free, NPR reports. Religious leaders once believed vaccinations were part of a plot to sterilize Muslim children; some vaccinators were even shot and killed. International finger-wagging and public campaigns reversed the trend, with Nigeria nearly eliminating polio in 2010.

There are still difficulties, however: Even as Nigeria edges closer to July 24, the Boko Haram-controlled north remains difficult or impossible to monitor for new cases of the disease.