Ebola infections will treble to 20,000 by November if efforts to tackle the outbreak are not stepped up, the World Health Organization has warned.
A new analysis suggests about 70% of those infected have died, higher than the 50% previously reported.
There have been 2,800 deaths so far and the disease remains “a public health emergency of international concern”, the UN agency said.
Trials of experimental drugs are being fast tracked in West Africa.
And more than 160 NHS staff have volunteered for UK efforts to help in the outbreak.
UK staff will be based at a 62 bed treatment centre in Sierra Leone, said chief medical officer for England, Prof Dame Sally Davies.
And she confirmed at a meeting of UK experts in London that the British nurse who survived Ebola, William Pooley, has volunteered to give blood that could help treat patients.
Meanwhile, more information on the spread and likely scale of the epidemic has emerged.
Projections published in The New England Journal of Medicine suggest by early November there will have been nearly 20,000 cases.
A new analysis of confirmed cases suggests death rates are higher than previously reported at about 70% of all cases.
And WHO scientists said numbers were predicted to rise exponentially, raising the possibility that the disease could become endemic [regularly found] in West Africa.
Nearly all of the deaths in the world’s worst Ebola outbreak have been recorded in Guinea, Liberia and Sierra Leone.
Dr Christopher Dye, Director of Strategy for WHO, said projections suggest “unless control measures – including improvements in contract tracing, adequate case isolation, increased quality of care and capacity for clinical management, greater community engagement, and support from international partners – improve quickly, these three countries will soon be reporting thousands of cases and deaths each week”.
Dr Dye, co-author of the study, called for “the most forceful implementation of present control measures and for the rapid development and deployment of new drugs and vaccines”.
It came as The Wellcome Trust charity announced that experimental drugs would be tested in West Africa for the first time.
Several drugs are under development, but they have not been fully tested and most are in very short supply.
They include the drug ZMapp, which has been given to a handful of infected health workers.
Dr Peter Horby, of the Centre for Tropical Medicine and Global Health at the University of Oxford, said the first trials could begin in West Africa as early as November.
“We want to evaluate these carefully, properly, in affected countries in West Africa,” he told the BBC.
“For the next one or two weeks we’ll be doing site assessments and we’ll be working with the WHO on identifying which drugs to prioritise, and then there’ll be a number of steps in setting up the systems – getting ethical approval through the countries and getting community participation and agreement to run the trials.
“Currently our wish is that we would hope to be able to enrol some patients sometime in November – that would be extremely quick by most clinical trial standards.”
Dr Jeremy Farrar, director of the Wellcome Trust, said therapeutics alone were not an answer.
“The answer really is public health interventions,” he said. “But I do think vaccines and drugs are going to play a role.”
