GENEVA, September 16. /ITAR-TASS/. The Ebola virus outbreak has killed more than 2,500 people in West Africa while 5,000 were infected, the World Health Organisation's assistant director-general Bruce Aylward said on Tuesday.

A senior UN coordinator for Ebola David Nabarro said Tuesday $1 billion is now needed to fight against the deadly Ebola virus.

"The amount for which we requested was about $100 million a month ago and now it is $1 billion, so our ask has gone up 10 times in a month," Nabarro said.

As the Ebola outbreak is advancing, “the level of surge we need to do is unprecedented, it is massive," he added.

Almost 40% of new infection cases happened in the past 21 days, the UN said. The mortality rate in the affected countries is estimated at around 60 or 70%, the organization said.

According to the World Health Organization (WHO), 22.4 million people currently live in the areas where the virus is being actively transmitted.

The Ebola virus outbreak has killed more than 2,500 people in West Africa while 5,000 were infected, the World Health Organization’s assistant director-general Bruce Aylward said on Tuesday. Most of those killed by the disease are in Guinea, Liberia and Sierra Leone.

WHO officials expect several thousand more cases in Liberia over the next three weeks.

The worst-ever Ebola outbreak began in December 2013 in Guinea. Cases have also been reported in Nigeria, where eight people died, and in Senegal, where one patient is being treated in hospital.

The Ebola virus disease (formerly known as Ebola haemorrhagic fever) was first reported in 1976 in Zaire (now Democratic Republic of Congo) and took its name from the river, in the northern Congo basin of central Africa, near which the first outbreak occurred.

It is a severe, often fatal illness, with a case fatality rate of up to 90% The infection is transmitted by direct contact with the blood, body fluids and tissues of infected animals or people. Severely ill patients require intensive supportive care.