Ten new cases and seven deaths from the virus were reported in Guinea since Wednesday, adding to the 291 reported cases and 193 deaths.
In Sierra Leone, the 50 total cases includes 34 new cases reported on Thursday. Six people have died from Ebola.
An individual suspected of being infected with Ebola died on Thursday in Liberia. The body was sent to Sierra Leone for burial. Officials from both Liberia and Sierra Leone are investigating the case.
In response to the continuing epidemic, WHO noted on its website that with its partners, they "have deployed experts to both Sierra Leone and Guinea to support and build capacity of national personnel to mount an effective EVD outbreak response including coordination, disease outbreak investigation, risk assessment, establishment of treatment facilities, case management, infection prevention and control in the newly affected districts, and social mobilization targeting the resistant communities."
Symptoms of the Ebola virus include fever, bruising, hearing loss, diarrhea, vomiting and bleeding. It is spread by close contact and kills up to 90 percent of its victims. The large geographical range of the reports of incidents, and the relatively porous borders between African nations, has helped spread the virus. There is no known cure or antivirus.