Mallard ducks in Maryland have tested positive for bird flu, apparently a common, less pathogenic strain that poses no risk to humans, the U.S. Agriculture and Interior departments said on Friday.

The H5N1 avian influenza virus was found in fecal samples from "resident wild" mallards in Queen Anne´s County in Maryland, on the U.S. central Atlantic coast.

"Testing has ruled out the possibility of this being the highly pathogenic H5N1 strain that has spread through birds in Asia, Europe and Africa," said USDA in a statement. "Test results thus far indicate this is low pathogenic avian influenza, which poses no risk to human health."

Five to 10 more days will be needed for definitive tests to confirm whether low-pathogenic H5N1 bird flu was found in the United States for the second time this year. On August 14, the virus was found in two mute swans in Michigan. Scientists say low pathogenic avian influenza commonly occurs in wild fowl.

The Maryland mallards did not appear sick so the samples, collected on August 2 as part of a research project, were not given high priority when sent to USDA labs for testing.

"The birds are alive and well," said a USDA spokeswoman.

The low-pathogenic strain of H5N1 has been found six other times in the United States since 1975. Mild and low pathogenic strains of bird flu are common in the United States and other countries.

Maryland Flu Preparedness