WASHINGTON (AFP) - A flock of 54,000 turkeys exposed to a non-lethal strain of bird flu virus will be destroyed, Virginia state officials said Tuesday.

Antibodies to the virus, which is not harmful to humans, were found during routine testing on the weekend prior to slaughter, Virginia's agricultural service said in a statement.

"This is not the severe, highly pathogenic strain that has caused widespread flock destruction and some human cases in countries outside of the United States," state veterinarian Richard Wilkes said in a statement.

"This is almost certainly one of the many milder strains of avian flu that are not uncommon in poultry and that cause only minor sickness or no noticeable symptoms in birds," he said.

None of the birds showed signs of illness and none entered the human food supply, nor will they once they are destroyed on site, said a spokesman for the Virginia Department of Agriculture.

Migrating birds can infect domesticated birds with a form of the virus that can infect humans, sometimes fatally.

However, epidemiologists' greatest fear is that the virus will mutate into a strain that can be transmitted from human to human and trigger an epidemic.

The virus found in Virginia is a weak pathogen, unlike the H5N1, which has prompted the destruction of 250 million birds worldwide, largely in Asia.

More than 300 people in Asia have been infected with bird flu virus since 2003, 190 of whom have died from the disease.

The display or sale of live fowl has been banned in Virginia until the end of July, an agriculture departure spokesman told AFP.

The measures taken in Virginia conform to the US federal policy to eradicate any H5 or H7 bird flu outbreak to prevent the possibility of the virus mutating into a more virulent strain, he said.

The United States has so far been spared of the H5N1 virus.

US authorities regularly test livestock fowl as well as a large number of wild birds, especially those coming from Asia and Europe.