The boy from Ha Nam province was admitted to a Hanoi hospital on March 11, and died on Friday night. Medical tests confirmed that the victim was infected with the lethal H5N1 strain.

His death is thought to have been caused by eating infected chicken meat. The boy's family raises chickens at their home, and 10 of them died in late February. Some healthy chickens from the flock were slaughtered for food.

Vietnam ranks second after Indonesia in bird flu fatalities, with an overall death toll of around 52 since the lethal H5N1 virus was first reported in the country in 2003. A total of 11 out of the country's 64 provinces have reported bird flu outbreaks. The two main sources of infection are the country's northern Thai Nguyen and central Quang Binh provinces.

This is the country's fifth death this year from bird flu, which has so far killed 235 people out of 371 confirmed cases worldwide, according to the World Health Organization.

Health experts in Vietnam warned that the H5N1 virus seems to have intensified with fatality rates growing to over 90%, against 50-60% in previous years.

However, the government said on its animal health department website that chicken owners were failing to report when their animals died or became ill, and even ate sick birds, which had led to deaths.

Although there have been no incidences of human to human infection, experts fear that it may mutate into a form that could easily be transmitted from person to person, causing a global pandemic.