For more than a week now a deadly tide has been washing out of China into the sea surrounding Hong Kong, bringing with it growing fears that China is in the grip of a covered-up bird-flu outbreak.

A melee broke out in northern Vietnam when more than 100 villagers prevented authorities from destroying chickens to stop the spread of bird flu, officials said Sunday as the country announced its second H5N1 case.

European scientists on Wednesday said they had uncovered how the influenza virus is able to take over human cells and use them as machinery to replicate itself.

Three of the 21 dead birds that recently washed up on Hong Kong's shores tested positive for the deadly strain of bird flu, the government said Wednesday.

Hong Kong health officials were investigating Wednesday whether 21 dead birds that recently washed up on the territory's beaches came from mainland China, where five people have died of bird flu this year.

Public health officials have expressed concern over a possible surge in influenza cases due to flu virus mutations as people return to work and schools reopen next week.

Some 220 million doses of Tamiflu, the vaccine against bird flu, are in the hands of governments worldwide, the Swiss pharmaceutical giant Roche said Wednesday.

Experts in Hong Kong were carrying out tests Tuesday on dead birds washed up on beaches amid fears of a large unreported avian-flu outbreak in neighboring mainland China.

Vietnam's capital city Hanoi has banned the use of motorcycles and bicycles to transport live poultry as part of efforts to protect the city from a bird flu outbreak.

The public should maintain high alert against the influenza virus after the massive flow of travelers during and in the wake of the long Chinese New Year holidays, according to public health officials.