The number of Ebola cases in west Africa could surpass 1.4million by January and the disease could become endemic, scientists warned in two separate reports published on Tuesday.
The World Health Organisation said that, unless "drastic improvements in control measures" were made, the number of cases - currently 5800 - could nearly quadruple to 21000 by the end of next month.
Christopher Dye, the head of strategy at the WHO and a co-author of the study, said: "We have rather modestly only extended the projections to November 2, but if you go to January 2, you're into hundreds of thousands."
He said it was feared that the virus, which has killed more than 2800 people this year in the deadliest outbreak in history, could become a "permanent feature of the human population".
The research by the UN-funded agency also found that the death rate in the current outbreak might be higher than calculated - closer to 70% than 55%.
The WHO study echoed a "worst-case scenario" report from the US Centres for Disease Control and Prevention.
It warned that, without significant increases in international efforts to stem the spread of the virus, some 1.4million could be infected by January.
The organisation also reported that the number of health workers killed by the disease had increased.
The agency said that, as of September 22, a total of 348 healthcare workers were known to have developed Ebola and 186 of them had died.
Half of the cases were in Liberia and 67 in Guinea which, along with Sierra Leone, have been worst hit by the outbreak.
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