A leading Chinese expert on respiratory diseases has warned the public to be aware that poultry can be infected with the bird flu virus but show no symptoms.

"Special attention should be paid to such animals, including those that have been vaccinated," said Zhong Nanshan.

"The existing vaccines can only reduce the amount of virus, rather than totally inactivating it," he said.

Zhong, an academician at the Chinese Academy of Engineering, is one of the scientists who helped control the spread of the Severe Acute Respiratory Syndrome, or SARS, in China in 2003.

His warning comes after eight human cases of the H5N1 strain of avian influenza have been reported across the country since January.

Zhong said he had noticed that more than half of those infected had no direct contact with birds and nor did they live in the areas where infected fowl with symptoms were reported.

He urged people to minimize contact with all domestic fowl and birds.

"Have the chicken butchered in the market, not in your home," he said.

A study led by Zhong on a low-cost treatment for chronic respiratory disease has been voted the people's choice for last year's paper of the year in The Lancet, the United Kingdom-based general medical journal.

(Xinhua News Agency February 6, 2009)