The top UN official for avian influenza says some of the $1.9 billion pledged by nations in January is already reaching nations struggling with the H5N1 virus. His remarks came at the end of a visit to China.

The U.N. system coordinator for influenza, David Nabarro, said the $1.9 billion pledged by nations and organizations at a donor conference in Beijing is reaching far and wide to places where people are battling the spread of H5N1.

"A lot of that money is now being spent in countries, in Indonesia, in Vietnam, in Cambodia, in countries in central and eastern Europe such as Turkey, Nigeria, and also Central Asia," said Nabarro.

The money is meant to fund education and other efforts to prevent the spread of the disease which, the World Health Organization says, has killed at least 107 people since 2003.

The U.N. official earlier told reporters that Africa remains an area of special concern. He said African nations need more funding and support to fight the disease.

H5N1 has been spreading steadily in Africa in recent weeks, mainly among domestic poultry, following warnings from world health officials that weak health care infrastructures and seasonal bird migrations might contribute to the spread of the disease.

Officials this week confirmed that Burkina Faso was the fifth African nation to register a case in poultry. Nigeria, Niger and Cameroon have also had outbreaks in birds, while Egypt has confirmed two human deaths from the virus.

Nabarro said the onset of warmer weather in the northern hemisphere is no guarantee that the threat of a further spread has passed, as evidenced by continuing outbreaks in the warm climates of Africa.

The subject of combating avian influenza was also on the agenda for U.S. Homeland Security Secretary Michael Chertoff, who wrapped up a visit to Asia with a stop in Beijing.

The U.S. official said he had discussed with Asian governments the importance of cooperation, to make sure the world is prepared in the event that H5N1 becomes easily passable from human to human.

"We need to start thinking way ahead of such possibility, of what we would do internationally to make sure we address this if it happened, and address this in a way that didn't break our fundamental economic trade and travel systems," said Chertoff.

Almost all of the human cases of H5N1 have involved transmission of the virus from animal to human. Scientists and health officials worry that the disease might mutate and become easily transmissible from human to human, raising the threat of a worldwide pandemic.