The World Health Organization (WHO) said on Tuesday the Ebola infection rate could soon reach 10,000 a week as world leaders prepared to hold talks on the crisis at the United Nations.
WHO assistant director general Bruce Aylward, describing his figures as a working forecast, said the epidemic "could reach 5,000 to 10,000 cases per week by the first week of December".
The latest death toll is 4,447, from 8,914 recorded cases of infection, Aylward said as the epidemic spirals in the three hardest-hit west African countries of Liberia, Sierra Leone and Guinea.
While the figures suggest a survival rate of 50%, they mask the true picture, Aylward said, adding: "What we're finding is 70% mortality" in all three countries.
The United Nations was due to hold talks later Tuesday on a public health crisis that the WHO has called the "most severe in modern times".
On Monday, US President Barack Obama and UN secretary general Ban Ki-moon called for the international campaign against the haemorrhagic virus to be intensified.
Meanwhile, a 56-year-old Sudanese doctor who had worked as a UN volunteer in Liberia died of Ebola on Monday night after arriving in Germany last week for treatment.
'No one taking care of us'
In Liberia, doctors and nurses pressed on with a strike demanding danger money to treat Ebola patients as the government threatened to fire them.
"Those who stay home... will be replaced and will never come back to work," health minister Walter Gwenigale said on state radio.
Ninety-five Liberian health workers have died so far in the epidemic, and their surviving colleagues want pay commensurate with the acute risk of dealing with Ebola, which spreads through contact with bodily fluids and for which there is no vaccine or widely available treatment.
In the face of the strike, the local office of the WHO said it was "very concerned for the safety and well-being of the Ebola patients, and urges the health workers to continue with their work".
In the capital Monrovia, a hospital patient quoted on local radio described scenes of desolation, with the sick deserted by striking staffers.
The unnamed man said patients who could still walk were climbing over the fence to escape from the treatment unit.
At least two cases of contamination have been reported beyond west Africa, in the United States and Europe.
Both have involved health workers who fell ill despite stringent safety protocols surrounding Ebola.
Read:India ramps up Ebola screening at airports
In Dallas, a nurse who tested positive after caring for a Liberian Ebola patient -- who died last Wednesday -- is in isolation and said to be in stable condition.
A Spanish nurse, Teresa Romero, 44, is thought to have caught Ebola while treating an elderly missionary who was infected in Sierra Leone and died on September 25.
A doctor at the specialist tropical disease hospital Carlos III in Madrid told reporters: "Statistics show that usually the disease is most deadly up to the 13th or 14th day. Now it is one day after that, so that is good."
$25mn for 'heroic work'
Facebook co-founder Mark Zuckerberg on Tuesday announced a $25 million donation to the US Centers for Disease Control Foundation to help US efforts to contain the epidemic.
"Grants like this directly help the frontline responders in their heroic work," Zuckerberg said on his Facebook page.
British troops began loading a ship that will set sail for Sierra Leone later this week to help in efforts to contain the outbreak.
The civilian-staffed military ship will travel with three helicopters, air crews and engineers to provide transport and support to medical teams and aid workers.
Measures have been introduced in the United States, Canada and Britain to screen for possible Ebola infections among passengers arriving at airports from African countries hit by the virus.
Asian aviation hub Singapore said it would also step up Ebola screening for passengers arriving at Changi Airport.
The UN nuclear agency said it would send specialised equipment to the west African countries hit by the Ebola outbreak to help faster diagnosis.
The machine uses the so-called Reverse Transcriptase Polymerase Chain Reaction technology that allows the Ebola virus "to be detected within a few hours, while other methods require growing on a cell culture for several days before a diagnosis is determined", the IAEA said.
"Early diagnosis... if combined with appropriate medical care, increases the victims' chance of survival and helps curtail the spread of the disease by making it possible to isolate and treat the patients earlier," it said in a statement.