Health and veterinary experts have singled out Indonesia, Egypt and Nigeria as countries where the risk of bird flu contagion is particularly worrisome.

FAO's Chief Veterinary Officer Joseph Domenech said important results have been achieved in Asia, Europe and the Middle East. He said that in places where the H5N1 virus was introduced during the past six months, it was rapidly detected and eliminated or controlled.

But he warned that, although the response to the deadly H5N1 virus in poultry has significantly improved over the past three years, the virus remains entrenched in several countries and will continue to spread.

But Domenech also stressed that there should be absolutely no reason for complacency.

"The H5N1 virus is not stable and keeps constantly changing. On one occasion in China last year a new virus strain appeared with different immunologic characteristics which made it necessary to modify the vaccines used in the region concerned. This emergence of a new strain may have happened again more recently in Indonesia."

The new disease is causing a lot of concern. A new respiratory disease that causes flu-like symptoms may be spread by bats. The virus was discovered in three members of a family in Malaysia last year. The Melaka virus, named after the place it was discovered, is not believed to be a killer virus, but its symptoms of fever and respiratory illness are severe and it's easily passed on to others.