WHO gave a period of 42 days, which is double the normal incubation time of the Ebola virus, to ensure that there are no new cases in the country.
Africa’s most populous country won praise for its swift response after an infected Liberian diplomat brought the disease there in July.
Nigeria had 20 cases of Ebola after a Liberian-American man named Patrick Sawyer flew into Lagos collapsed at the airport. Health care workers treating Sawyer were infected, and as it spread it ultimately killed eight people, a low number next to the thousands of cases and deaths in other countries. Nigeria’s health system is considered more robust, but there was significant concern from experts that a case would pop up in one of the country’s dense-populated slums and catch fire.