Surveillance programme finds avian influenza in the US

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

The swans were sampled as part of the expanded avian influenza surveillance programme. They were showing no signs of sickness, which suggests that this is low pathogenicity avian influenza. Additionally, genetic analysis of the virus conducted at USDA's National Veterinary Services laboratories (NVSL) in Ames, Iowa, suggests that it is similar to a low pathogenicity strain that has been found in North America.

"This is not the highly pathogenic avian influenza virus that has spread through other parts of the world," said Dr Ron DeHaven, chief of the Animal and Plant Health Inspection Service at the Agriculture Department. "We do not believe that it represents a risk to human health."

Because federal and state game rangers and university ornithologists are testing thousands more birds since Congress approved $29 million for expanded bird flu screening, Dr DeHaven said it was 'no surprise' that the virus had been found.

It is possible that these birds were not infected with an H5N1 strain, but instead with two separate avian influenza viruses, one containing H5 and the other containing N1. The confirmatory testing underway at NVSL will clarify whether one or more strains of the virus are present, the specific subtype, as well as pathogenicity. These results are expected within two weeks and will be made public when completed.