More than $1bn (£618m) is needed to fight the West Africa Ebola outbreak - a tenfold increase in the past month, the UN's Ebola co-ordinator has said.David Nabarro made the announcement as the World Health Organization (WHO) described the health crisis as "unparalleled in modern times".
It has killed 2,461 people this year, half of the 4,985 infected by the virus, the global health body said.
There has been criticism of the slow international response to the epidemic.
Joanne Liu MSF presidentHighly infectious people are forced to return home, only to infect others and continue the spread of this deadly virus”
Later, the US president is to announce plans to send 3,000 troops to Liberia, one of countries worst-affected by the outbreak, to help fight the virus.It is understood the US military will oversee building new treatment centres and help train medical staff.
Medical charity Medecins Sans Frontieres (MSF) called on other countries to follow the US lead as the response to outbreak continued to fall "dangerously behind".
The outbreak began in Guinea before spreading to its neighbours Sierra Leone and Liberia.
Nigeria and Senegal have reported some cases, but seem to have contained the transmission of the virus.
Infected ' turned away' "We requested about $100m a month ago and now it is $1bn, so our ask has gone up 10 times in a month," Mr Nabarro told a briefing in Geneva.
"Because of the way the outbreak is advancing, the level of surge we need to do is unprecedented, it is massive."
At the briefing WHO deputy head Bruce Aylward announced the new Ebola case figures.
"Quite frankly, ladies and gentlemen, this health crisis we're facing is unparalleled in modern times. We don't know where the numbers are going on this," he said.
When the WHO had said it needed the capacity to manage 20,000 cases two weeks ago "that seemed like a lot", Dr Aylward said.
"That does not seem like a lot today," he added.
At the same briefing, MSF president Joanne Liu said there needed to be "co-ordinated response, organised and executed under clear chain of command".
Sick people in the Liberian capital were banging on the doors of MSF Ebola care centres desperate for a safe place in which to be isolated, she said.
"Tragically, our teams must turn them away; we simply do not have enough capacity for them," Dr Liu said.
"Highly infectious people are forced to return home, only to infect others and continue the spread of this deadly virus. All for a lack of international response."
Earlier on Tuesday, the WHO welcomed China's pledge to send a mobile laboratory team to Sierra Leone, which will include epidemiologists, clinicians and nurses.
"The most urgent immediate need in the Ebola response is for more medical staff," WHO head Margaret Chan said in the statement.
Ebola virus disease (EVD)
- Symptoms include high fever, bleeding and central nervous system damage
- Spread by body fluids, such as blood and saliva
- Fatality rate can reach 90% - but current outbreak has mortality rate of about 55%
- Incubation period is two to 21 days
- There is no proven vaccine or cure
- Supportive care such as rehydrating patients who have diarrhoea and vomiting can help recovery
- Fruit bats, a delicacy for some West Africans, are considered to be virus's natural host