West Africa has had its first Ebola-free week, with no known cases, since the epidemic began in March 2014, the World Health Organization said Wednesday.
But the W.H.O. has warned that Ebola could still come back because more than 500 people in Guinea who may have been exposed are still being monitored and will not be in the clear until a 21-day incubation period is over.
In addition, health officials have lost track of some people who were considered high-risk contacts in Guinea and Sierra Leone.
In those countries and Liberia, there have been a total of 28,421 cases, with 11,297 reported deaths since the outbreak last year.