The U.S. Departments of Agriculture and Interior today announced final test results, which confirm that an H5N1 avian influenza virus detected in fecal samples collected last month from resident wild mallard ducks in Maryland is a low pathogenic subtype. This strain has been detected several times in wild birds in North America and poses no threat to human health.

The USDA National Veterinary Services Laboratories (NVSL) confirmed the presence of the "North American strain" of low pathogenic H5N1 avian influenza through virus isolation in samples collected from the resident wild mallards in Queen Anne´s County, Maryland. Test results announced on September 1 indicated that an H5N1 avian influenza subtype was present in nine of the collected samples, but further testing was necessary to confirm pathogenicity. As previously announced, genetic testing ruled out the possibility that the samples carried the specific highly pathogenic strain of H5N1 avian influenza that is circulating overseas.

Low pathogenic strains of avian influenza commonly occur in wild birds and typically cause only minor sickness or no noticeable signs of disease in birds. Low pathogenic H5N1 is very different from the more severe highly pathogenic H5N1 circulating in parts of Asia, Europe and Africa. Highly pathogenic strains of avian influenza spread rapidly and are often fatal to chickens and turkeys.

The Departments of Agriculture and Interior are working collaboratively with States and academic institutions to sample wild birds throughout the United States for the presence of highly pathogenic avian influenza. More than 21,000 wild birds have been tested so far this year and none have been infected with highly pathogenic avian influenza.