The death toll from the Ebola virus outbreak has risen to 4,447, with the large majority of victims in West Africa, the World Health Organization (WHO) says.
WHO assistant director-general Bruce Aylward also said there could be up to 10,000 new cases a week within two months if efforts were not stepped up to contain the spread of the disease.
But the rate of new infections in some areas has slowed down, he added.
Sierra Leone, Liberia and Guinea have been hardest hit by the outbreak, the BBC reports.
There have been 8,914 cases overall, including the fatal cases, and the WHO said it expects this number to top 9,000 by the end of the week.
The WHO estimates its figures by taking the numbers of confirmed cases and multiplying them - from Guinea by 1.5, from Sierra Leone by 2 and from Liberia by 2.5 - to account for under-reporting.
Mr Aylward said WHO was concerned to see the virus was still spreading in the capitals of the three worst-affected countries.
He said the death rate in the current Ebola outbreak was 70 percent, describing it as a "high-mortality disease".
He said 95 percent of cases were limited to areas in the "historic epicentre" of the outbreak, where the rate of new infections appeared to be slowing.
However, he stressed that it would be too early to read this as success.
The latest WHO projections suggested there could be between 5,000 and 10,000 cases a week in Guinea, Liberia and Sierra Leone by December.
Countries neighbouring the three worst-affected states are "at risk" and it is important for them to prepare for the possibility of Ebola cases, the WHO said.
UN worker dies in Germany
A United Nations worker being treated for Ebola in Germany has died.
The man, believed to be Sudanese doctor, arrived in Germany for treatment last week.
He had been working in Liberia and is the second member of his UN team to die from the virus.
Doctors in the clinic in Leipzig where he was being treated said they used experimental drugs in a bid to save the man's life.
He was also placed in a hermetically-sealed isolation ward, accessed through airlock systems.
The man was one of three Ebola patients being treated in Germany.
A Sengalese aid worker treated in Hamburg has made a full recovery and a Ugandan doctor is still being treated in Frankfurt.