By Louisa Lim
BBC News, Beijing
A 10-year-old Vietnamese girl has died from avian flu, according to local health officials.
Vietnam has been worst hit by the latest outbreak
The girl, who lived in Hanoi, is believed to be the 50th recorded death from the virus in Asia since the latest outbreak hit in January 2004.
Vietnam has seen 36 of those deaths, while Thailand has lost 12 people and Cambodia two.
Experts are worried the virus could eventually combine with human flu and risk a deadly pandemic.
Nguyen Hai Yen, 10, died on 27 March in St Paul's Hospital in Hanoi, Le Van Diem, director of the hospital, told the BBC Vietnamese service.
"As soon as the patient was admitted to our hospital, her conditions became very serious and the patient passed away. The later test result from the National Institute of Hygiene and Epidemiology confirmed it was the H5N1 virus," he said.
H5N1 BIRD FLU VIRUS
Principally an avian disease, first seen in humans in Hong Kong, 1997
Almost all human cases thought to be contracted from birds
Isolated cases of human-to-human transmission in Hong Kong and Vietnam
The government last week announced a nationwide clean-up of poultry farms, to try to stop the spread of bird flu.
The Ministry of Health said that large commercial operations and small local farms in every village in Vietnam would be disinfected.
North Korea is the most recent addition to the list of Asian countries hit by bird flu. But its poultry have been infected with the H7 strain of the virus, which is less deadly to humans.
The strain that has decimated poultry stocks and caused recent human deaths in Cambodia, Thailand and Vietnam is the more virulent H5N1 strain.