WASHINGTON (Reuters) - A second round of tests on swans in Michigan confirmed the birds have a low-pathogenic strain of H5N1 and not the deadly avian influenza virus that has killed more than 141 people in Asia, Europe and Africa, the U.S. Agriculture Department said on Monday.
Routine tests conducted in a Michigan gaming area earlier this month found two of about 20 swans had what was believed to be a low-pathogenic strain of H5N1.
"Genetic testing confirms that these swans were not carrying the highly pathogenic strain of H5N1 avian influenza that is circulating overseas," USDA said in a statement.
The swans had shown no sign of sickness, which indicated this was low pathogenicity avian influenza. Pathogenicity refers to the ability of the virus to produce a disease.
A low-pathogenic strain, which produces less disease and mortality in birds than does a high-pathogenic version, poses no threat to human health.
The low-pathogenic strain of H5N1 has been found six other times in the United States since 1975, most recently in 2002. It is common for mild and low pathogenic strains of bird flu to appear in the United States and other countries.
The infected swans were found as part of an increased surveillance program put in place after USDA received $91 million in supplemental funding from Congress for bird flu last December.
The H5N1 bird flu strain, which has killed an estimated 141 people and forced hundreds of millions of birds to be destroyed, has not been found in the United States
