Migrating birds may be responsible for the unprecedented spread of a highly contagious bird flu that has broken out across Asia, killed seven people and ignited fears of a deadly pandemic sweeping the world.
In a matter of weeks bird flu has broken out in South Korea, Japan, Taiwan, Vietnam, Cambodia, Indonesia and Thailand. Pakistan said on Monday it had also found the flu in some of its chickens.
Scientists are baffled by the wildfire spread of the disease, which the World Health Organization calls “historically unprecedented,” but one theory is wild birds are behind it.
“Migratory birds may explain the rapid spread of the virus in the region,” said Lo Wing-lok, an infectious disease expert in Hong Kong.
The flu has devastated chicken populations wherever it has appeared and killed six people in Vietnam and one in Thailand, but experts say there is no sign it is being passed between people. All the human victims are believed to have come into contact with sick chickens.
But the big fear is that the virus may attach itself to a human flu virus, mutate and spread between people.
The H5N1 bird flu virus first jumped the species barrier in Hong Kong in 1997. It killed six people but the outbreak was contained in the city and halted by a cull of its poultry.
This time it seems to have broken out more or less simultaneously in places thousands of kilometers apart.
“We don’t know how this virus is spreading and so it’s safe to presume that nowhere can consider itself safe,” Peter Cordingley, spokewsman for WHO's East Asia headquarters said. “The challenge is growing by the day.”
People warned to avoid wild birds
Hong Kong’s health minister, Yeoh Eng-kiong, warned residents to keep away from wild birds although the financial hub has been spared an outbreak of the virus so far.
“Wild birds may be infected and their feces are known to carry the virus, so people have to be careful,” Yeoh said.
A government spokeswoman added: “People who come in contact with wild birds must wash their hands thoroughly.”
While experts in Japan in mid-January dismissed as slim the likelihood of migratory birds carrying the disease to that country, wild birds were blamed for a small outbreak in Hong Kong from late 2002 and early 2003.
That winter, dead waterfowl were found infected with the virus in a park. Although workers moved in quickly to cull other birds in the Shatin park, chickens were found sick with the virus within days.
“The likely source of the infection of those birds are migratory birds landing in those parks,” said Lo.
China has not reported any incidents of H5N1 but authorities are wary.
“We are worried about the bird flu situation in neighboring countries because birds all have wings,” said an official at the State Forestry Administration in Beijing.
Many farms in Hong Kong are netted to keep out wild birds but nerves were jolted last week when authorities found a dead peregrine falcon ridden with the virus.
Officials do not know where the falcon came from although a handful of the migratory birds, which breed in Siberia, are known to spend the winter in the region around Hong Kong.