GENEVA — As the tally of deaths from the worst known outbreak of the Ebola virus continued its seemingly inexorable rise, the World Health Organization said Thursday that the epidemic was still accelerating and could afflict more than 20,000 people — almost seven times the current number of reported cases — before it could be brought under control.
The forecast was made as WHO reported the number of known cases and fatalities had risen once again. The organization also acknowledged that in areas of intense transmission “the actual number of cases may be two-to-four times higher than that currently reported.’’
The outbreak “continues to accelerate,’’ the organization said.
According to the latest figures released by WHO on Thursday, the death toll has risen by more than 100, to 1,552 out of 3,069 cases in four West African countries: Guinea, Liberia, Sierra Leone and Nigeria, which had previously indicated its outbreak was under control.
While the disease was first identified in March, “more than 40 percent of the total number of cases have occurred within the past 21 days,’’ WHO said. “However, most cases are concentrated in only a few localities.’’
The assessment came as WHO presented a road map for affected countries and for the international community that included strategies designed to deal with more than 20,000 cases, Bruce Aylward, an assistant director general of the health organization, told reporters in Geneva. The plans are likely to cost nearly half a billion dollars over the next six months.
The road map aims to stop transmission of the virus in the next eight to nine months, Aylward said, but he added: “We have to be realistic that there is uncertainty’’ about such targets.
With many centers for treating the disease now too full to take new patients, classic treatment strategies could no longer cope, and it was necessary to find and expand other complementary approaches to contain the spread of the disease, the organization said.
The road map assumes that a number of countries that are not now affected by the epidemic could become so, but it also asserts that the procedures it sets out could stop any new transmissions within eight weeks of the first case being identified.
“That’s extremely aggressive,’’ Aylward said, acknowledging that such speedy containment had only ever been achieved in remote locations, not in the crowded urban centers now affected.
The road map came as Tom Frieden, director of the U.S. Centers for Disease Control and Prevention, warned that the epidemic could get worse before it gets better. Frieden called for quicker international help and cooperation to control its spread.
In a sign of the difficulties facing governments seeking to contain the disease, the health authorities in Nigeria reported for the first time Thursday that the disease had spread beyond Lagos, its commercial capital, to claim another death.
Nigeria does not share a land border with the other three countries in the grip of the outbreak.
The first sign of the virus’ spread to Nigeria came when Patrick Sawyer, a Liberian-American traveling from Liberia, flew to Lagos and died of the disease in the teeming city last month. Nigeria is Africa’s most populous nation but has recorded only 15 patients infected with Ebola, six of whom have now died.
The Nigerian health minister, Onyebuchi Chukwu, told reporters Thursday that a man who had come into contact with Sawyer had evaded surveillance and traveled to Port Harcourt, the hub of Nigeria’s lucrative oil industry in the south of the country, where he infected a doctor who later died.
The man, who was not identified by name, recovered from the disease. The wife of the dead doctor also has Ebola symptoms, Chukwu said, according to The Associated Press. Additionally, 70 people in Port Harcourt, including funeral directors who embalmed the dead doctor, are now under surveillance.
In its statement Thursday, WHO said the countries hit hardest by the epidemic — Guinea, Liberia and Sierra Leone — were “struggling to control the escalating outbreak against a backdrop of severely compromised health systems, significant deficits in capacity, and rampant fear.’’
Aylward, picking out details of the road map, said it would need at least 750 international and 12,000 local health workers, not in capital cities but “right out there in the districts running the operations.’’
“That is very difficult in the current environment,’’ he added, alluding to fears arising from the high number of medical workers — 250 as of Monday — who had contracted the disease.
Recruiting international staff may be harder than finding local personnel, he added, debunking the notion that locals were running away from the crisis.
Health workers were getting infected because they were exhausted from working extraordinary hours, Aylward said.
“The best way to get this program safer is to get a lot more people into these countries,’’ he said.
The road map emphasized the need to halt transmission of the disease in major cities and ports and underscored the importance of keeping air and shipping links operating to deliver medical supplies, personal protection equipment, food and other goods to fight the outbreak.
Guinea, Liberia and Sierra Leone are facing severe economic downturns as they struggle to cope with the Ebola outbreak, the African Development Bank reported Thursday, a problem that is likely to be exacerbated by the growing number of airlines cutting services to those countries. On Wednesday, British Airways said it was suspending flights to Liberia and Sierra Leone because of Ebola concerns. Air France followed suit Thursday.
WHO was already arranging short-term air support with the World Food Program to offset flight cancellations by commercial airlines, Aylward said, but the cost of the response would rise sharply if this had to become a long-term arrangement.
“Bans on travel and trade will not stop this virus, absolutely not; in fact you are more likely to compromise the ability to respond,’’ Aylward said. “It’s a self-defeating strategy.’’