No sign of Asian bird flu in Michigan swans

(Aug 29, 2006) Bird flu found in a wild swan in Michigan was not the deadly Asian strain that has ravaged poultry and killed at least 141 people worldwide, the Agriculture Department said on Monday.

Final tests confirmed the swan had a mostly harmless, low-pathogenic strain of the H5N1 virus, officials said.

Authorities found bird flu in two mute swans Aug. 14, but only one of the samples had high enough levels of flu to allow confirmatory tests. Earlier genetic analysis ruled out the more virulent Asian strain in both birds.

The low-grade strain has been found many times in North American wild birds and poses no threat to people, the department said. Confirmatory tests were done by the department's National Veterinary Services Laboratories in Ames, Iowa.

The swans were the first reported in the government's effort to test as many as 100 000 wild birds to determine if the virulent Asian H5N1 strain has arrived in North America. Officials expect the virus to reach the continent this year.

The sampling was expanded earlier this month from Alaska to the entire US. Among the first targets were 20 mute swans from a game area in Monroe County, Michigan. Testing found the possibility of H5N1 in two of the swans.

Any finding of highly pathogenic H5N1 in wild birds in the US would prompt more intensive monitoring and extra security measures to protect commercial poultry flocks from infection.

Deadly, highly pathogenic strains spread rapidly and are usually fatal to chickens and turkeys, the department said, while low pathogenic H5N1 generally causes little sign of sickness in birds.

Since 2003, the virulent H5N1 strain has been blamed for the death or destruction of millions of birds overseas. Nearly all the people who have been infected had close contact with sick birds or their droppings. However, scientists fear the virus could mutate into a form that is spread easily among humans. (from


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