GENEVA, May 26, 2009 (AFP) - There has been a "dramatic upsurge" in yellow fever in the Central African Republic and has affected more than 30 countries where the disease was previously not a threat, UN agencies said Tuesday.

"In the last few years, we've seen a resurgence of the circulation of the yellow fever virus" in Africa and Latin America, said Rosamund Lewis, project leader of the World Health Organisation's yellow fever initiative.

The surge came as funding for vaccine stockpiles is running out, the UN health agency and Unicef said.

Lewis said health agencies are facing a shortfall of US$186 million (S$269 million) in funding for vaccination campaigns in Ghana and Nigeria, which count among countries at the highest risk from the disease.

"However, we're also seeing a dramatic upsurge in yellow fever virus circulation in the Central African Republic which has had a number of cases in the past year," she said.

"We're seeing new cases in countries both in Africa and in Latin America that have not seen cases in 40 years or have ever documented cases," said Lewis, citing Brazil as an example of the Latin American countries.

"Whereas we're talking about 186 million to finish Ghana and Nigeria, there are actually 22 countries still at risk in Africa and 11 countries at risk in Latin America after that," she added.

Yellow fever is caused by a mosquito-transmitted virus.

Some 206,000 cases of the disease and 52,000 deaths occur annually, according to WHO estimates.