It "will need one little chance ... and this could give rise to a serious virus," Dr. Ken Shortridge, a microbiologist at the University of Hong Kong who is heading an investigation into the flu outbreak, told Radio Television Hong Kong.
The latest outbreak of bird flu prompted authorities to order the slaughter of about 170,000 chickens at three farms. About two dozen farms were put under quarantine after fresh reports of infections.
The exact number of chickens killed by the virus was not available Wednesday, though earlier reports said more than 30,000 birds had died.
Bird flu does not usually affect humans. However, the discovery of a new outbreak fanned fears that it could turn out to be H5N1-97, a virulent type of flu virus that crossed over to humans in 1997, killing six people.
Last May, a similar avian virus infected thousands of chickens, forcing the government to destroy 1.37 million birds. That outbreak did not affect humans.
Lily Yam, secretary for environment and food, said in a radio interview Wednesday that tests of blood and offal samples from the dead chickens only indicated the cause of the deaths as H5 avian flu. The exact strain would only be identified next week, she said.
Some recent tests found samples containing H5N1 virus, but it was not the same type as the one that proved infectious for humans in 1997, Yam said.
In the radio interview with Radio Television Hong Kong, Shortridge said the virus was mutating quickly and could develop into a deadly strain, although it was not an immediate threat to humans.
Shortridge did not return calls from The Associated Press.
The latest outbreak comes at a particularly bad time for local poultry sellers, who count on a boost in sales from Lunar New Year feasts that usually feature chicken. Local reports said sales of live chickens had plummeted by as much as 80 percent since the outbreak began.
Housewife Kan Choi-ying said she would serve roast pork and vegetables rather than chicken during the holidays.
"I won't buy any chicken at all, no matter whether it's fresh or frozen," Kan said. "I don't want to die."
Hong Kong's 6.9 million residents consume about 100,000 chickens daily, traditionally preferring to buy their chickens live from cages in street markets and bring them home freshly killed.
Poultry markets were ordered closed on Friday for cleaning.
Some critics blamed the repeated outbreaks on overcrowding, poor hygiene and a lack of ventilation at local chicken farms, though the government has stepped up inspections and cleaning of markets in recent years.
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