HONG KONG, CHINA (APRIL 2, 2013) (REUTERS) - Hong Kong health officials urged vigilance over a strain of bird flu previously unknown in humans, as China confirmed four new cases in eastern China on Tuesday (April 2).
The strain has already killed two people, raising the total number of known cases to seven.
The World Health Organisation (WHO) said on Monday there was no evidence that the H7N9 strain could be transmitted between people, but that it was investigating the outbreak.
The four new patients in China's eastern Jiangsu province were all in critical condition and receiving emergency treatment, the Xinhua News Agency said, citing the Jiangsu provincial health bureau. A woman in Anghui province who caught the virus in early March is also in critical condition.
"From the information we obtained from the World Health Organisation as well as from the mainland, we noticed that this H7N9 virus is avian flu virus. Obviously, it has been, undergone, some kind of mutation so that it now can infect human beings," said Leung.
Hong Kong saw the world's first case of H5N1 avian flu in 1997. The outbreak, that killed six, was contained after authorities culled about 1.5 million chickens.
But the new H7N9 variation is not highly pathogenic or deadly among birds, Leung said.
"H7 is usually a low pathogenic virus. In other (words), it's less likely to kill birds or chicken. The main implication is we may not see a large number of deaths among birds or chickens, and then cases of, human cases, appear," Leung said.
"Most of the people in close contact with these people have not got infected. So, it doesn't seem to be highly transmissible. But clearly, this has to be investigated further and of course it's important also to know whether, where, exactly this virus is coming from because, so far, human infection is coming from an animal or bird source," he said.
China's National Health and Family Planning Commission on Sunday confirmed a Xinhua report that three people had been infected with the new strain.
The two deaths were men in Shanghai aged 87 and 27 who fell sick in late February.
It is not known how the seven victims were infected, though the government believes the virus is not highly contagious.