Will "bird flu" strike North America?

• Position: Medicine & Health

A virulent strain of avian influenza (H5N1), deemed by the World Health Organization to be "the most serious known health threat facing the world," could be heading to North America. "Bird flu" already has killed at least 60 people of 115 confirmed cases in Southeast Asia since the end of 2003 and has spread to Mongolia, Tibet, Siberia, and Kazakhstart. Should a serious strain of avian influenza arrive here via people, poultry, or wild birds, it could have major implications, caution researchers at the University of California, Davis.

Avian influenza is an infectious disease of birds that was first identified in Italy more than 100 years ago. It now is found worldwide. Wild waterfowl and shorebirds, particularly ducks and geese, commonly carry various strains of avian influenza but usually are not killed by it. However, wild birds have been implicated in the spread of flu to domestic birds, especially ducks, chickens, and turkeys. In domestic birds, avian influenza can induce severe illness and death. Avian flu also has spread to domestic pigs and zoo tigers and leopards in Asia.

H5N1 first was diagnosed in a person in Hong Kong in 1997. Subsequent deaths have sparked concern that a worldwide influenza pandemic could develop.

Scientists believe that the conditions of animal agriculture in Asia have given rise to...