WASHINGTON, D.C. ? 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 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.