A Vietnamese man has become the latest victim of the disease, taking Asia's death toll to 19. A team of experts from Hong Kong has arrived in Vietnam for closed-door meetings with local health officials and the WHO in an attempt to contain the outbreak.

The experts caution that up to 70 percent of people who have caught bird flu in the latest Asian outbreak have died from the virus, around twice the level from the 1997 outbreak in Hong Kong.

With data suggesting an affected range of 60 to 70 percent, one member of the expert team from Hong Kong expressed shock at the nature of the epidemic.

According to respiratory medicine specialist David Hui, "This time it appears to be much more rampant compared to before, and many cities are affected. So we are actually quite concerned."

But he added that it was still unclear why this H5N1 strain was more lethal, or why only two countries had reported human deaths.

"This is a puzzle... we are trying to find out: Is the virus changing in structure? Is it becoming more virulent? Is the clinical spectrum different from 1997?" Hui added.

He said that in 1997, the bird flu outbreak in Hong Kong had a mortality rate of 30 percent, killing six people.

This time, bird flu has been reported in 11 countries--both the deadly H5N1 strain as well as milder versions, like the H7 that was detected this weekend in the US.

Japan has temporarily banned chicken imports from the US following the discovery of bird flu in Delaware.

For a country which is heavily dependent on imports for its food needs, Japan's Agriculture ministry said on Sunday that it was trying to confirm the nature of the disease in Delaware.

If the latest strain is not harmful to people, the Japanese government might consider lifting the ban on poultry from the US.

(CCTV February 10, 2004)