As of Monday, the organization recorded a total of 200 suspected or confirmed cases of Ebola, which is normally found in central or eastern Africa, in Guinea, Liberia and Mali. The bulk of the cases are in Guinea, and Mali has yet to have a confirmed case. Tests are ongoing.
The deaths of 121 people in Guinea and Liberia have been linked to the disease.
There is no vaccine and no cure. Officials have said the current outbreak could last months. Health care workers are isolating the sick and tracking down anyone they have come into contact with.