A Chinese man, who was the first case of bird flu in the country in more than a year, has died in the southern city of Shenzhen, according to health officials.
The 39-year-old bus driver was admitted to hospital with pneumonia but tested positive for the bird flu virus.
The H5N1 bird flu strain has a high level of mortality, killing up to 60% of humans infected with it.
Positive tests on a dead market chicken last week prompted nearby Hong Kong’s government to issue an alert.
Hong Kong authorities culled 17,000 chickens after three birds were found to have died from the H5N1 bird flu strain.
It also banned imports and the sale of live chickens for three weeks after the infected chicken carcass was found at a wholesale market.
But it was not clear whether the chicken came from a local farm or was imported.
The Shenzhen victim had not been in contact with poultry, nor travelled recently, China’s Ministry of Health told Hong Kong health authorities.
In November 2010, a 59-year-old woman was isolated in Hong Kong with bird flu but survived.
In October 2011 a 29-year-old woman confirmed to have contracted the virus died on the Indonesian island of Bali.
The World Health Organization says bird flu has killed 332 people since 2003.
The virus has been eliminated from most of the 63 countries infected at its 2006 peak, which saw 4,000 outbreaks across the globe, but remains endemic in Bangladesh, China, Egypt, India, Indonesia and Vietnam.
China’s Ministry of Agriculture warned last month that the bird flu virus seemed to exist widely in the poultry markets of mainland China, particularly in the south.
Meanwhile, the World Health Organization has expressed deep concern about the way research was being carried out on the H5N1 virus, which can be fatal if transmitted to humans.
Such work carried significant risks and must be tightly controlled, said the WHO.
Scientists in the Netherlands and the US said last week they had discovered ways in which the virus might mutate so it can spread more easily to – and between – humans and other mammals.
The US government has asked the scientists not to publish full details, in case the information is used to produce a biological weapon.