A Vietnamese duck farmer has become the first person to die of bird flu in Vietnam in nearly two years, while another death from the disease was reported in neighboring Cambodia.

Vietnamese officials said Thursday the 18-year-old farmer from the southern Mekong delta died after reporting a high fever and respiratory problems. Investigators have not determined whether he was infected by his flock.

Meanwhile, Cambodian officials said a two-year-old boy also died of the avian influenza on Wednesday after being exposed to sick or dead poultry.

The virus usually only infects humans that come into direct contact with diseased birds.

Since the H5N1 strain of avian influenza was first detected in 2003, it has killed at least 340 people worldwide.

At the peak of the outbreak in 2006, the virus had spread to 63 nations, before it was eradicated in most of those countries due to a mass culling of domestic poultry.

The virus has killed 17 people in Cambodia and nearly 60 in Vietnam. Human bird flu cases have recently been reported in China, India, Indonesia and Egypt.

Some scientists fear H5N1 could mutate into a form readily transmissible between humans, with the potential to cause millions of deaths.