March 6, 2009

An outbreak of the deadly H5N1 bird flu virus at a Hong Kong farm last year that led to the slaughter of 90,000 chickens was likely spread by wild birds, an investigation found Thursday (March 5).

The December outbreak was the first to be discovered at a Hong Kong poultry farm in six years, and raised fears about the city's biosecurity measures or whether the deadly H5N1 virus had mutated.

Thomas Sit, the head of the government's investigation team, said they couldn't be totally sure what had caused the outbreak.

"As with many epidemiological studies of this nature, it is difficult to determine the exact cause of the outbreak," Sit told reporters.

But he said the virus was "most likely to have been introduced to the farm by wild birds."

The dust and dirt near the entrance of one of the two affected chicken sheds could have been contaminated by the droppings from infected wild birds, and then blown into the shed area by wind, Sit said.

Sit said the farmer, who ran one of the city's major poultry farms, had been warned to improve biosecurity measures, but wouldn't face any further action.

Hong Kong was the scene of the world's first reported major bird flu outbreak among humans in 1997, when six people died. Since then, H5N1 has killed more than 250 people worldwide.

Scientists fear the virus could mutate into a form which is much more easily transmissible between humans, triggering a global pandemic that could kill millions.