A 20-year-old Cambodian woman who was rushed to a Vietnamese hospital with suspected bird flu, died Wednesday, the World Health Organization (WHO) said.

The woman from Kampot province had been taken across the nearby Vietnamese border suffering a high fever and respiratory problems, symptoms of the H5N1 virus that has killed 51 people in Asia, Vietnam’s Tuoi Tre newspaper said.

“We know that a Cambodian woman went to hospital in Vietnam and died in Vietnam but there is no confirmation yet that she died of bird flu,” said Megge Miller of the WHO in Phnom Penh.

Test results from samples taken by doctors at the Kien Giang provincial hospital and sent to Ho Chi Minh City’s Pasteur Institute 155 miles away should be available Thursday, she added.

Three Cambodians from Kampot province have already died of the bird flu virus, along with 12 Thais and 36 Vietnamese. The Vietnamese newspaper quoted the girl’s relatives as saying chickens had died of unknown causes near her home.

Health experts fear the virus could mutate into a form that can pass easily among humans and millions could die in a global pandemic. Cases in places like Cambodia, where health and monitoring systems are rudimentary, only sharpen the fears.

The virus is now endemic in several areas of Southeast Asia and Vietnam, the country hit hardest, says it does not expect to be able to contain bird flu until at least 2007 because the way it is spreading still baffles experts.