The UK's plans to deal with bird flu are "as good as if not better" than other leading nations, the government's adviser on infectious diseases says.
China has culled thousands of poultry after outbreaks of bird flu
Professor Roy Anderson said the Department of Health was backed up by a "very strong" scientific community.
He added that the greatest danger was that the H5N1 virus could mutate to become a human variation lies in China.
Meanwhile, Health Secretary Patricia Hewitt has said the threat to the UK was "very low".
She said: "The World Health Organisation - to whom I spoke only a few days ago - confirmed that the threat to the general population in Britain from bird flu is very, very, very low indeed."
Prof Anderson said conditions in China were conducive for the strain to mutate.
But he said it was "comforting in one sense" that since the virus appeared in 1996 there had been no such mutation.
No human deaths have been reported in China, but thousands of infected poultry have been culled.
The H5N1 strain has killed at least 60 people since 2003.
Professor Anderson said that while it was likely bird flu would spread into Western Europe, it would not increase the risk of a human strain occurring as "that's more likely to occur in China."
He said there were three reasons for this:
- the density of ducks, geese and chickens per human is very, very high there
- the social environment is such that humans have great intimacy with their poultry livestock
- the H5N1 virus is endemic throughout large parts of China
Professor Anderson said the risk was that if a person with human flu became infected with bird flu, the resultant strain could have the disease-causing properties of bird flu with the transmissibility of human flu.
"In the long timescale of decades it is probably certain that it will happen," he told the BBC.
He said Britain's plans to cope with an outbreak of both bird flu in poultry and a human strain were "as good as, if not better" than other leading countries, and developing all the time.
Two parrots have died in quarantine in Britain and a nationwide ban on the sale and display of birds at markets and fairs around England is in place.
H5N1 BIRD FLU VIRUS
Principally an avian disease, first seen in humans in Hong Kong in 1997
Almost all human cases thought to be contracted from birds
Possible cases of human-to-human transmission in Hong Kong, Thailand and Vietnam, but none confirmed
Meanwhile, the Department for the Environment, Food and Rural Affairs has ordered that the pigeon and poultry section of the Countryside Live fair in Harrogate be cancelled this weekend because of fears over the disease.
Event organiser Bill Cowling said he was disappointed that the birds, mainly bantams bred for display, had been banned.
"This would have been the first major show of the winter showing season.
"But all the exhibitors we have spoken to have been supportive of the action.
"They think that if the government thinks there's a risk, their experts have perceived a risk, we should be supportive of them at this stage to try to eliminate that risk."
BIRD FLU OUTBREAKS IN 2005 (H5N1 STRAIN)
The H5N1 strain remained largely in South-East Asia until this summer, when Russia and Kazakhstan both reported outbreaks
Scientists fear it may be carried by migrating birds to Europe and Africa but say it is hard to prove a direct link with bird migration
UK case discovered in quarantine, so disease-free status unaffected