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Abstract
Waterfowl from northwestern Minnesota were sampled for Avian Influenza Virus (AIV) from July October in 2007 and 2008. AIV was detected in 222/2,441 (9.1%) ducks in 2007 and in 438/2,452 (17.9%) ducks in 2008. AIV prevalence peaked in late summer. We detected 27 and 28 subtypes during 2007 and 2008, respectively. Ten hemagglutinin (HA) and all neuraminidase (NA) subtypes were detected each year. Subtype diversity varied between years and increased with prevalence. There were seven predominant subtypes detected during 2007 (>5% of subtype diversity), and six predominant subtypes detected during 2008. Within H2 and H12, H2N3 and H12N5 viruses predominated, respectively, but each were only detected during a single year. Mallards were the predominant species sampled, and 531 AIV were isolated from mallards (80.5% of total isolates). Juvenile mallard data from both years adequately described the temporal and spatial prevalence from the total sample and also adequately represented subtype diversity.