The death toll from the Ebola epidemic rose to 4,922 out of 10,141 known cases in eight countries through Oct. 23, the World Health Organization (WHO) said on Saturday.

The three worst-hit countries of West Africa - Guinea, Liberia and Sierra Leone - account for the bulk, recording 4,912 deaths out of 10,114 cases, the WHO said in its update.

The overall figures include outbreaks in Nigeria and Senegal, deemed by the WHO to be now over, as well as isolated cases in Spain, the United States and a single case in Mali.

the true toll may be three times as much: by a factor of 1.5 in Guinea, 2 in Sierra Leone and 2.5 in Liberia, while the death rate is thought to be about 70 percent of all cases.

Explaining these projections, the WHO said many families are keeping infected people at home rather than putting them into isolation in treatment centers, some of which have refused patients due to overcrowding.

The UN agency, sounding an ominous note, said that out of the eight districts of Liberia and Guineasharing a border with Ivory Coast, only two have yet to report confirmed or probable Ebola cases. The WHO says 15 African states including Ivory Coast are at highest risk of the deadly virus being imported.