HANOI (AFP) - Vietnamese state media on Saturday announced that a man had died of bird flu, the country's first human death from the disease since November 2005.

The 20-year-old from Ha Tay province, bordering Hanoi, died of the H5N1 strain on Sunday, June 10, at the capital's National Contagious and Tropical Diseases Hospital, said the official Vietnam News Agency.

The latest death brings to 43 the number of people who have died of the human form of bird flu in Vietnam.

"The man was diagnosed (with) catching the virus on June 2 and moved to the Hanoi hospital six days later," the report said.

"He became the first Vietnamese to die of the deadly virus after 17 months (during which) the country successfully contained the epidemic."

Four other people have been reported infected with the H5N1 strain of the virus in Vietnam. Two have recovered and two are undergoing treatment, state media has previously reported.

None of Vietnam's five reported human infections, including the fatality, has yet been officially confirmed by the World Health Organisation (WHO).

Communist Vietnam, once the country worst hit by the disease, contained earlier bird flu outbreaks through mass vaccination campaigns, culls of millions of poultry, and public education campaigns.

But the virus has come back strongly this year, hitting scores of poultry farms in an unusual summer-time outbreak, especially in the densely populated northern Red River delta region in recent weeks.

Avian influenza outbreaks have been reported since early May across 18 of Vietnam's 64 provinces and municipalities, mostly among unvaccinated ducks and other waterfowl.

Neighbouring China has stepped up anti-bird flu measures in its southern Guangxi region, which shares a 600-kilometre (400-mile) border with Vietnam, vaccinating birds, closing markets and banning cross-border poultry trade.

The UN Food and Agriculture Organization (FAO) recently blamed the surge on a rise in often unvaccinated ducks grazing in newly harvested rice paddies after Vietnam in March lifted a ban on waterfowl hatching.

Experts warn that ducks can be "silent carriers" of bird flu, spreading the virus through their faeces as they roam across rice fields and ponds while seldom showing symptoms of illness themselves.

The FAO warned Vietnam must ensure good surveillance and response mechanisms, that vaccination campaigns must match breeding cycles and that hatcheries, slaughterhouses and markets must be clean.

WHO's Vietnam communications officer Dida Connor, speaking in Hong Kong Friday before news of the man's death, said Vietnam was responding to the fresh outbreaks but also cautioned against complacency.

"I am sure there is a feeling of confidence in the way the situation has been handled in the past," she said. "That's positive. Now is the time people need to recognise that it can change at any moment."

"This is not going to go away," Connor said. "There is a sense of complacency which is potentially catastrophic if it was to increase."

Worldwide, the virus has killed 191 people out of 313 infected patients, according to the WHO. Experts fear the death toll would multiply rapidly if the virus were to mutate and become easily transmitted between humans.