Abuja – Nigeria has been declared Ebola-free, following the World Health Organization’s announcement that Senegal is now rid of the virus. Nigeria was thrust in the Ebola spotlight in July after an infected air traveler introduced the virus to the capital city of Lagos. The case spurred fears that the disease would spread through Africa’s most populous country. WHO credits an aggressive government response and effective contact tracing for keeping the virus in check. For WHO to declare an Ebola outbreak over, a country must pass 42 days with active surveillance in place, supported by good diagnostic capacity, and with no new cases detected, the agency said. The 42-day period is also twice the maximum incubation period from Ebola.