A farmer transports cages of live chickens to a local market in Hung Yen Province, Vietnam (03 Jun 07)

Health officials in Vietnam say bird flu has killed a teenage boy, the country's second death in a little more than a week.

Officials confirmed Tuesday that the 15-year-old boy died Friday in Hanoi, and tested positive for the deadly H5N1 strain of the virus.

His death was the fourth for Vietnam this year. On July 31, a 22-year-old pregnant woman also died from the disease.

Vietnam once had the world's highest rate of bird flu infections and death, but the government managed to contain outbreaks through mass vaccination campaigns, culling millions of birds, and public education campaigns.

Despite those efforts, the virus came back strongly this year and has hit poultry farms across the country.

The World Health Organization says 95 other people have contracted the bird flu virus since 2003 in Vietnam, 42 of whom have died.

The WHO says close contact with dead or sick birds is the principal source of human infection.