Hanoi  - A 3-year-old Vietnamese boy has died of avian influenza after four days in hospital, a health official said Friday, bringing Vietnam's bird-flu death toll to three this year.

   Nguyen Van Chau, director of the Ho Chi Minh City Health Department, said the boy from the south-western province of Dong Thap died Thursday. He had been admitted Monday at the Ho Chi Minh City Hospital for Tropical Diseases with high fever and respiratory difficulties.

   Chau said the boy and his parents ate a duck several days ago. His department and provincial health officials were disinfecting the area around the boy's house, he added.

   The government-run newspaper Vietnam News reported Friday that the Preventive Medicine Centre had sent fluid samples from the boy's family members and local poultry farmers to be tested for H5N1, the strain of avian influenza that can be deadly in humans.

   The infection was the first human case of bird flu reported in Vietnam's south so far this year.

   There have been three confirmed cases of bird flu in northern Vietnam, two of whom died in February. The third patient's older sister died of symptoms consistent with avian flu in January but was not tested.

   There have been 106 confirmed human H5N1 infections in Vietnam since it first appeared in the country in late 2003. Fifty-three of the patients died.

   The disease is usually spread by contact between infected birds and humans, but scientists fear that the virus could mutate into a form that is easily transmissible among humans and spark a global pandemic that could kill millions.