A man in southwestern China has died of bird flu, health authorities said Saturday, becoming the second fatality from the H5N1 virus this year.

The 31-year-old died in hospital in the city of Guiyang on Friday, the Guizhou province health department said in a statement, adding that no other human cases of avian flu had been reported in the province.

Another city resident, a 21-year-old woman, died from the virus earlier this month.

The Xinhua news agency said both of them had come into close contact with birds but it was not known if the cases were related.

The H5N1 virus typically spreads from birds to humans through direct contact, but experts fear it could mutate into a form transmissible between humans with the potential to trigger a pandemic.

More than 365 people have died of bird flu globally since the virus re-emerged in 2003, according to the World Health Organization.

Its figures show that China saw 25 deadly cases of the virus between 2003 and 2009 before numbers tailed off to one fatality in each of the three following years. The deadliest year of the past decade in China saw eight deaths in 2006.

China is considered one of the nations most at risk from bird flu epidemics because it has the world's biggest poultry population and many chickens in rural areas are kept close to humans.

China has in the past been accused of covering up the extent of bird flu outbreaks, exacerbating fears when new cases are reported.

Separate outbreaks among birds were reported last year in the northern region of Ningxia and the remote northwestern region of Xinjiang, prompting massive culls of chickens.