By SABIN RUSSELL
San Francisco Chronicle
September 29, 2005
The strain of bird flu known as H5N1 has yet to mutate into a form that can be transmitted easily among humans, but it already poses a threat to people in Asian nations who live in close proximity to ducks and chickens, and it would cause huge problems for the U.S. poultry industry if H5N1 became established in North America.
During the summer, the virus was apparently carried by migrating birds from China and Southeast Asia to Kazakhstan and Siberia, in the Russian Federation, where it subsequently infected domestic chicken flocks. The more entrenched the virus becomes in the world's bird population, experts believe, the greater the chances H5N1 will eventually mutate into a human disease.
Unlike seasonal flu, this influenza strain has been extraordinarily deadly for the few humans who have caught it from close contact with infected birds. Since December 2003, when the outbreak began, 115 people are known to have contracted it, and 59 of them died in four Asian countries.
At a meeting in Washington, D.C., with health leaders from North and South America on Tuesday, World Health Organization Director-General Dr. Lee Jong-wook declared that a pandemic was virtually inevitable. "There is a storm brewing that will test us all," he said. "We must anticipate it and prepare to the very best of our combined abilities."
At the University of California-Davis Medical Center in Sacramento, doctors and bird veterinarians outlined efforts under way in California to monitor the dangerous H5N1 strain, which has yet to appear in birds in the Western Hemisphere, but is bound to create a scare if and when it does.
The focus is currently on Alaska, a junction where birds from the East Asia/Australian flyway - encompassing areas infected with H5N1 - can make a left turn and fly south along the Pacific Americas Flyway, which runs along the Pacific Coast, through California, all the way to the southern extreme of Argentina.
"Ducks, geese, gulls and terns are a natural host for these viruses," said Dr. Walter Boyce, executive director of the Wildlife Health Center at the university.
He stressed that research so far has shown no evidence of any wild bird carrying the H5N1 virus in North America. But with the seasonal migrations of millions of birds now kicking into gear, Boyce said there is a concern that wild birds "will spread H5N1 around the world."
Dr. Carol Cardona, an avian flu and poultry expert at the university, said the arrival of H5N1 will be problematic for chicken producers in the United States, but because birds here are raised under different conditions from those in Asia, it is less likely to wipe out vast flocks of domestic birds.
In Asia, farmers live in close proximity to many small flocks of birds where ducks, geese, chickens and pigs intermingle. In the United States, most poultry are raised in large commercial establishments that require standard "biosecurity" procedures limiting human contact with bird feces, which carry the virus.
Such biosecurity procedures have in fact worked in Asia. To date, the H5N1 virus has not turned up in the large poultry farms and processing plants that operate there, Cardona said.
In the United States, the arrival of H5N1 will necessitate tighter surveillance for bird flu, and flocks found infected would be "depopulated," the veterinarian said. But she does not anticipate that orders would come down requiring the widespread slaughter of poultry - even those that are raised in backyards and on hobby farms. As scary as this virus is, common sense procedures such as covering bird feed piles and keeping chickens under a roof can protect birds from virus dropped by wild, infected birds.
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