Low pathogenicity avian influenza subtypes isolated from wild birds in the United States, 2006-2008.

Due to concerns that high pathogenicity avian influenza would enter into the United States, an interagency strategic plan was developed to conduct surveillance in wild birds in order to address one of the possible pathways of entry. The USDA and state wildlife agencies participated in this effort by collecting samples from 145,055 wild birds from April 2006 through March 2008 in all 50 states. The majority (59%) of all wild bird samples was collected from dabbling ducks, and 91% of H5 detections using real-time reverse transcriptase polymerase chain reaction (rRT-PCR) were in dabbling ducks. Apparent prevalence of H5 by rRT-PCR in all birds sampled was 0.38%. Most (48%) H5 detections were found in mallards (Anas platyrhynchos). Thirty-three virus subtypes were identified; H5N2 was the most prevalent subtype and accounted for 40% of all virus isolations. We present the virus subtypes obtained from the national surveillance effort and compare them with research results published from various countries.