Posted on 01/28/2004 8:15:22 AM PST by blam
'Virulent avian flu bug puts humans at risk'
January 28 2004 at 09:00AM
By Tan Ee Lyn
Hong Kong - The unusually large number of ducks dying from avian flu in southern China indicates that the virus has become more virulent, which will put more people at risk of contracting it, Hong Kong scientists said on Wednesday.
They also raised the alarm about chilled and frozen poultry meat, saying the deadly H5N1 virus could survive for years in temperatures as low as -70°C, but repeated that it can be killed if meat is cooked properly.
China confirmed on Tuesday that H5N1 had killed ducks in southern Guangxi province, making it the tenth place in Asia to be afflicted with a disease that has killed eight people in the region in the last few weeks.
"H5 viruses are generally less fatal to ducks, so it is uncommon for so many ducks to die. This means this particular H5N1 strain has become more virulent," said virologist Leo Poon from the University of Hong Kong.
"This means it can cause extensive deaths in poultry and this may in turn increase the chance of more people contracting it (if they come in direct contact with sick birds)."
The flu has devastated poultry populations wherever it has appeared, and the greatest fear is that the H5N1 avian flu virus might latch onto human influenza and unleash a pandemic among people with no immunity to it.
The avian flu strain first jumped from chicken to human in 1997 in Hong Kong, infecting 18 people and killing six of them. Then, experts considered ducks to be the original host of the H5N1, although the waterfowl were usually not taken ill by the bug.
Scientists said they could not rule out the possibility that the new, more powerful bird flu strain might make the jump from human to human less difficult. So far, most of those infected were in close contact with chickens at home or on farms.
"If virulence goes up, it would trigger larger outbreaks and more poultry deaths and this increases the chance of human to human transmission," Poon said.
Hong Kong has already banned the import of chicken from places affected by the bird flu, and Poon urged the government to begin stringent checks on chilled and frozen chicken and ducks in stores and warehouses and on future imports.
"We must check the source of chilled and frozen chicken and we must do it at once," Poon said.
Although the virulence of the current strain indicates the virus has mutated, experts were divided over whether the vaccine used in Hong Kong and parts of mainland China to inoculate chickens against the bird flu is still useful.
The vaccine was cultured from the milder H5N2 virus.
"It still serves to prevent H5N1," Poon said.
But Frederick Leung, dean of science at the University of Hong Kong, was more circumspect.
"This H5N2 vaccine provides cross-protection and effectiveness in 80 percent of chickens. But it is based on the 1997 strain. If there has been a mutation, any scientist will tell you the protection will be less than 80 percent, or even none," Leung said.
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