"Africa is not ready. We have lots of concern," the WHO's regional director for Africa, Luis Gomes Sambo, told Reuters.

He said the WHO is urging African nations to budget more state funds for detection of the highly pathogenic H5N1 virus, which is endemic in poultry across Asia. It has infected 124 people in Asia and killed 64.

Sambo said the WHO also would call on the United Nations and the World Bank to pitch in money to improve surveillance of chickens in Africa's rural hinterlands where scientists say the virus could easily spread undetected.

A UN food agency expert said last month that East Africa was more vulnerable to bird flu than Europe and its lack of preparedness causes grave concern.

"The risk is there, and we must get the countries prepared to make a response against an epidemic," Sambo said after giving a speech at Harvard Medical School.

"We are keeping the governments informed of the developments. We keep our fingers crossed," he said.

The most vulnerable area is East Africa's Rift Valley, where impoverished rural populations are already struggling under the twin burdens of AIDS and malaria.

Birds migrating from Asia to the northern hemisphere for the winter stop over in freshwater ponds and lakes along the Valley - a vast geographical and geological feature that runs north to south for 3,100 miles (5,000 km) from northern Syria to central Mozambique.

"There are reasons to think it will spread to Africa as it has already been spread to Europe thanks to migrations," said Marc Lipsitch, assistant professor of epidemiology at the Harvard School of Public health.