Most human cases have been traced to contact with sick poultry, but experts fear the virus could mutate into a form that is easily transmissible among people, sparking a pandemic.
The latest deaths were a 26-year-old man from Cambodia's southern province of Kampot and a 17-year-old woman from Vietnam's northern Nam Dinh province.
The man died of the severe H5N1 strain, according to test results from Phnom Penh's Pasteur Institute, Deputy Agriculture Minister Yim Voeun Tharn said.
That strain of bird flu began ravaging Asian poultry farms in December 2003, and also has claimed 48 human lives — two of them Cambodians, 12 from Thailand and 34 from Vietnam.
In Vietnam, the teenager, who died Thursday, was one of two new bird flu cases reported Friday. In addition, a 40-year-old woman was hospitalized in stable condition in Hanoi, health officials said.
An epidemiologist for the World Health Organization in Cambodia, Megge Miller, said this week's Cambodian victim, Meas Ran, was believed to have contracted the disease from poultry that died near his house. Villagers did not immediately tell authorities about the sick chickens for fear that their remaining stock would be slaughtered, Miller said.
The 40-year-old woman and her family ate chicken March 10 and she began developing the disease's typical symptoms of fever, coughing and labored breathing four days later, said Nguyen Van Thich with Quang Ninh province's medical center said.
In Vietnam, where 14 people have died of bird flu since December, the latest cases follow a string of infections that have had health experts worried about the spread of the virus now acknowledged to be endemic in the region.
Officials are unsure how the teenager contracted the disease because there had been no outbreaks among poultry in her village, said Vu Huu Viet, head of Nam Dinh's provincial medical center.