More than 20,000 people could become infected with the deadly ebola virus, the World Health Organisation has said.
The UN health agency warned the actual number of current ebola cases in hard-hit areas could be 12,000 - four times higher than the number confirmed at present.
In what amounted to be a bleak assessment of the disease, the WHO said it believed the virus was still being spread in a "substantial number of localities" and added that "the outbreak continues to accelerate".
It also expressed concern at the unprecedented number of health workers who have died after treating patients in West African countries including Liberia, Guinea, Nigeria and Sierra Leone.
The WHO's assistant director-general, Dr Bruce Aylward, said: "This far outstrips any historic ebola outbreak in numbers, as the largest outbreak in the past was about 400 cases.