However, Guangzhou Institute of Respiratory Diseases director Zhong Nanshan still insisted Friday that with adequate precautionary measures such as early discovery, diagnosis, quarantine and medication, a disaster can be averted.

He said that with cats and beech martens being infected in Germany, the alarm bells over a possible human pandemic have begun sounding.

"We are one step closer to human beings contracting bird flu as mammals are now being infected, and humans are, after all, mammals," Zhong said.

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He fears that once pigs started to carry the virus, the risk to humans will grow accordingly.

Hong Kong epidemiologist Lo Wing-lok said that among mammals, pigs are capable of playing host to a number of viruses such as swine flu, bird flu and even human influenza.

Should pigs contract the H5N1 virus, which happened in 1976 in the United States and in 2004 in Indonesia, they will become the mixing pots for the recombination of viruses.

"The reassortment of a new virus among pigs could likely spread among humans," he said.

But Lo said since pig farms in Hong Kong are licensed and no one has backyard pig farms, the risk of bird flu virus transmission through pigs is not high.

He urged people to pay attention to their personal hygiene and to avoid contact with poultry and pigs.

Zhong issued a reassuring message: "If people have prepared well, I don't think that there will be a great outbreak [of bird flu among humans]."

Hong Kong University microbiologist Ho Pak-leung said several overseas studies had revealed that many types of mammals could contract the H5N1 virus, especially rats and those from the feline family such as tigers, leopards and cats. He urged people not to allow their children to handle dead birds and to keep their cats, dogs and other pets away from wild birds.

In a related development, Zhong said that bird flu victims in the mainland were found to have weaker immune systems. He said mainland experts have not come to any conclusion and are still studying the relationship between the physical condition of the victims and their susceptibility to bird flu. Two Indonesian children have died of bird flu, bringing the country's toll to 22. A 12-year-old girl died on March 1 in Solo, a city in Central Java province and a boy, 3, died last week in the city of Semarang, also in Central Java.

Both appeared to have had contact with infected chickens.