FILE- In this Saturday, Jan. 22, 2011 file photo, a health worker injects a young boy with yellow fever vaccine in Seguela in northern Ivory Coast. On Thursday, May 19, 2016 the UN health agency convened an expert committee to consider whether the epidemic of yellow fever, an acute viral hemorrhagic fever, qualifies as an international public health emergency. (AP Photo/Olivier Asselin, File)

LONDON - The World Health Organization says the ongoing outbreak of yellow fever in central Africa is "serious and of great concern" but does not warrant being declared a global emergency.

On Thursday, the U.N. health agency convened an expert committee to consider whether the epidemic of yellow fever, an acute hemorrhagic disease, qualifies as an international health emergency. That is defined by WHO as an "extraordinary" event with the potential to cross borders and requiring immediate action.

WHO previously declared crises including the 2014 Ebola outbreak and the Zika virus to be global emergencies.

After deliberating for several hours, the committee's chair, Oyewale Tomori, announced that although yellow fever does not meet the conditions for being an international health emergency it requires "intensified control measures" including better surveillance and vaccination policies.

The current yellow fever outbreak, first identified in Angola last December, has sickened more than 2,000 people and killed nearly 300. The mosquito-spread disease has also been exported to Congo, Kenya and China.

There is no known treatment for yellow fever, but there is a vaccine, although global stocks are limited. Yellow fever is common in tropical parts of Africa and Latin America but until this year, had never jumped to Asia.

People with yellow fever often experience fever, muscle pain, and nausea. About 15 per cent of patients suffer a more toxic phase in a day and get jaundice, abdominal pain and kidney problems. Nearly half of those patients die within two weeks.

Some experts called WHO's decision not to declare a global emergency a mistake.

"Why should we have to wait until the crisis is right upon us before we act?" asked Michael Osterholm, an infectious diseases expert at the University of Minnesota. "Africa is like a gas can waiting for the yellow fever match to hit it."

He also predicted the disease would eventually make its way elsewhere, including to the United States.

Paul Reiter, an entomologist at the Institut Pasteur in Paris, described the world's ability to control mosquitoes as "absolutely zilch" and warned the situation in Africa could spiral into something "globally catastrophic." Reiter noted the same mosquitoes that spread yellow fever also transmit Zika and dengue — and cases of both have risen dramatically in recent months.

"I don't think we should dismiss the potential worst-case scenario of this epidemic," said Dr. Bart Janssens, director of operations for Doctors without Borders. "It's a very unusual situation."

He said yellow fever is now circulating in two African capitals — Luanda and Kinshasa — heightening the risk of its international spread.

News from © The Associated Press, 2016