Some 30 deaths were reported between Tuesday and Friday, WHO said.
The current Ebola outbreak began in Guinea in March and later spread to Sierra Leone and Liberia. Two people have died in Nigeria.
WHO earlier on Friday declared the outbreak an international public health emergency.
"The possible consequences of further international spread are particularly serious in view of the virulence of the virus, the intensive community and health facility transmission patterns, and the weak health systems in the currently affected and most at-risk countries," WHO said.
There is no licensed treatment or vaccine for Ebola and the death rate has been about 50%.