The H7N9 bird flu virus has spread to another province in the Yangtze River Delta, with Zhejiang health officials announcing two human cases yesterday, one of them fatal.
The national health commission said the source of infection remained unknown, but listed poultry workers or people who had been in contact with poultry a week before the emergence of symptoms as a high-risk group.
Hong Kong's government is considering the reintroduction of health declaration requirements for inbound travellers.
Video: The new strain of bird flu will spread across and beyond China unless the poultry source is identified and interventions taken quickly, a microbiologist warns.
A 37-year-old chef in Taicang, Jiangsu, fell ill on March 7 and went to Hangzhou, Zhejiang's provincial capital, for treatment on March 18.
He died in Xiaoshan Hospital on March 27.
A 67-year-old Hangzhou man was admitted to a hospital in the city on March 25 for a cough and a fever and was transferred to another hospital on Tuesday in a critical condition. He tested positive for the H7N9 virus yesterday.
"So far no epidemiological connection has been found between the two cases," Zhejiang's health department said.
Those who had been in close contact with the two patients were being monitored.
The new cases took the total to nine, including three deaths.
The six patients - four in Jiangsu, one in Anhui and one in Zhejiang - are all in a critical condition.
A diagnosis and treatment guideline issued yesterday by the National Health and Family Planning Commission said the source of transmission was unclear, but was probably from contact with discharges or faeces of poultry carrying the virus.
The guideline said no concrete evidence of human-tohuman transmission had been found and the high-risk group "are mainly people engaged in poultry farming, sales, slaughtering or processing or having contact with poultry".
Dr Zhong Nanshan, director of the Guangzhou Institute of Respiratory Diseases, said they were sporadic cases and not a cluster outbreak or epidemic. "It is quite different from what happened 10 years ago during the Sars (severe acute respiratory syndrome) epidemic," Zhong told the Beijing Times.
"The first and second cases of Sars were highly contagious and family members were infected.
"But the H7N9 flu has not shown any contagion, even though the confirmed cases are all very serious and the cause is not clear."
Gregory Hartl, spokesman for the World Health Organisation's influenza and epidemics division, said that as there was no evidence so far of human-tohuman transmission, "we're a long way away from thinking about a pandemic".
But he said lack of knowledge about the mode of transmission of the H7N9 virus had posed difficulties in controlling the disease.
In Hong Kong, Secretary for Food and Health Dr Ko Wing-man said there was no need yet to raise the city's pandemic response level, but the reintroduction of visitor health declaration forms was being considered.
Sampling of live chickens supplied to Hong Kong and at chicken farms has been stepped up, but tests are being carried out only for the H5 and H9 viruses.
In Taiwan, the health department designated the H7N9 virus a notifiable disease yesterday.
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