Vietnam confirmed its seventh human bird flu death in three weeks, prompting the UN health organisation to warn that the virus could turn into a global pandemic that would eclipse the devastation caused by last month's Asian tsunami.

A 47-year-old man from northern Thai Binh province died of bird flu in Hanoi on January 10, about 10 days after developing a high fever and coughing, officials said.

The victim's younger brother, who cared for him in the hospital, has also tested positive for bird flu and is in hospital in stable condition, able to sit up in his bed and talk.

With three new bird flu deaths confirmed this week, World Health Organisation (WHO) expressed concern about the high fatality rate - more than 70 per cent of those infected have died - and the lack of research to answer critical questions about how it is transmitted, especially since no vaccine or effective treatment exists.

"We've got to be very careful that we don't lose sight of, or control of, the bird flu health threat which could have much greater public health implications than the tsunami," said William L Aldis, the WHO's top representative in Thailand.

The string of deaths in Vietnam renewed concerns that the virus could combine with a human flu virus and create a new version that is easily transmitted among people, although there is no evidence this has happened yet.

Human cases generally have been traced to direct contact with sick birds.

But as more human bird flu cases occur, the chances become greater for the deadly virus to acquire more ability to be transmitted from person to person. That could spark the next global pandemic - possibly killing millions, WHO experts have warned.

"If we continue to experience these frequent new outbreaks with the virus spread both in poultry and people, it finally might result in an awful virus strain that could become a pandemic with a horrendous outcome," said Hans Troedsson, WHO's representative in Vietnam. "The more frequently we get outbreaks, the higher risk we have to infect." he said.

PHOTO CAPTION

Farmers watch a culling pit where thousands of their sick chickens are destroyed in the southern province of Long An. (AFP)