The World Health Organisation (WHO) predicts there will be a huge rise in Ebola cases in Liberia.
It said the disease is spreading “exponentially” in the country, and that thousands of people will become infected there over the next three weeks.
Conventional methods to control the outbreak were "not having an adequate impact", the UN's health agency added. It said organisations combating the outbreak needed to scale-up efforts "three-to-four fold".
The epidemic started in Guinea in February, and has since spread to Sierra Leone, Liberia, Nigeria and most recently Senegal. At least 2,100 have been infected, according to WHO estimates.
Of the five countries now affected, Liberia has been hit the hardest. According to WHO, the epidemic had caused 1,698 cases and 871 deaths there as of 31 August.
WHO reported sufferers being turned away from Liberian treatment facilities because they were so full.
"As soon as a new Ebola treatment facility is opened, it immediately fills to overflowing with patients, pointing to a large but previously invisible caseload," it said.
"When patients are turned away... they have no choice but to return to their communities and homes, where they inevitably infect others."
It added that the situation was particularly bad in Liberia's Montserrado county, where 1,000 beds were needed for infected Ebola patients but only 240 were available.
Why is Ebola spreading so fast in Liberia?
Understanding why the disease is spreading so much faster in Liberia than in other West African countries is crucial for tackling the outbreak.
Possible reasons already suggested include variations in burial practice, lack of communication of risk, and the poor state of the healthcare system since the 1999-2003 civil war.