Hanoi  - A Vietnamese boy has tested positive for the avian influenza virus, the fourth confirmed human case of bird flu in Vietnam this year, local media reported Thursday.

A boy from the south-western province of Dong Thap was admitted Monday at the Ho Chi Minh City Hospital for Tropical Diseases with high fever and respiratory difficulties, the Tuoi Tre newspaper said.

Nguyen Van Chau, director of the Ho Chi Minh City Health Department, told the paper that the patient tested positive for bird flu Wednesday.

The patient's condition was said to be worsening, and he is breathing with the help of oxygen machines.

Two of this year's earlier bird-flu patients died. In the third case, the patient's older sister had died of symptoms consistent with avian flu but was not tested.

There have been 106 confirmed human cases of bird flu in Vietnam since it first appeared in the country in late 2003; 52 of those infected 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. (dpa)