A Vietnamese man has died from bird flu, raising the country's death toll from the deadly virus to 39.

Health officials say the Hanoi resident died Tuesday after being hospitalized six days earlier. It was unclear how the man contracted bird flu.

The Vietnamese government says it will begin nationwide vaccinations of poultry in August in an effort to contain the spread of the virus, which has also killed 12 people in Thailand and four others from Cambodia.

Medical experts say the H5N1 virus that causes bird flu appears to be spread only by close contact between humans and infected poultry. However, they warn that bird flu could change into a form that can easily pass between people, triggering a global pandemic.