GENEVA - The risk of a mutation of the bird flu virus increases in winter, the season of normal human flu, the World Health Organisation said Thursday.
"The H5N1 virus does not sleep and still constitutes a danger," said Mike Perdue, a doctor from the WHO programme to fight influenza.
Migrating birds carry the virus and can infect poultry that are kept in the open, he said.
With many people infected with regular flu, the risk increases for a genetic adaptation of H5N1 that could be transmitted between humans, he added.
"It's impossible to predict if the virus is going to mutate. For now, it's not the case," he said, underlining that checks had significantly increased since last year.
More than 220 people have caught bird flu in Asia since the end of 2003 and 139 have died from the virus.
09/28/2006 19:19 GMT