GENEVA, August 28. /ITAR-TASS/. The number of people infected with the Ebola virus may surpass 20,000, the World Health Organization said on Thursday.

"The outbreak continues to accelerate. More than 40% of the total number of cases have occurred within the past 21 days," the UN health agency said in its roadmap plan issued to deal with the outbreak.

The total number of probable and confirmed cases in the current Ebola outbreak in the four affected countries (Guinea, Liberia, Nigeria, and Sierra Leone) is 3,069, with 1,552 deaths, the WHO reported.

"This Roadmap assumes that in many areas of intense transmission the actual number of cases may be 2-4 fold higher than that currently reported," the WHO said.

The WHO also said it needed $490 million to combat the disease outbreak over the next six months.

The deadly outbreak began in Guinea in March and spread to Liberia, Sierra Leone and Nigeria.