A 58-year-old man from Hanoi was admitted to a hospital in the capital on Aug. 24 and died the same day, said a doctor who identified herself only as Lien.
Pham Ngoc Dinh, deputy director of the National Institute for Hygiene and Epidemiology, said the man tested positive for the H5 component of the bird flu virus, but that the N1 element has not been determined. More tests are being conducted.
The man from Soc Son District ate duck a week before dying. It was purchased from a market, and no other family members became ill after eating the poultry, said Nguyen Van Loan, director of the district Preventive Medicine Center.
Loan said the man's house has been disinfected and blood samples of those who were in contact with him have been sent for testing.
There were no reported bird flu outbreaks among poultry in the district, he said.
The latest case brings Vietnam's human death toll to 43. Thailand has recorded 12 deaths while Cambodia and Indonesia have logged four and three, respectively.
The virus has killed or forced the slaughter of millions of poultry across Asia and has also recently reached Russia.
Vietnam has begun a mass poultry vaccination to try to slow the spread of the virus. The campaign is expected to reach about two-thirds of the nation's provinces by next month before winter begins.
Health officials have warned repeatedly that avian influenza could mutate and spread easily from person to person, sparking a global pandemic that could kill millions. So far, most human cases have been linked to contact with sick birds, the AP reports.