Figure 2.

Bar charts depicting combined subtypes of influenza A virus (IAV) isolates recovered from initial samples (replicate #1) of filtered surface water inoculated with paired cloacal and oropharyngeal swabs from ducks (a) and samples retrieved from field sites (replicate #2) after being maintained at ambient temperature in the field for a period of 209–229 days (b). Bars are shaded to represent subtype combinations for viruses isolated from samples from Alaska (white) and Minnesota (black). In two instances, a mixed infection was isolated upon initial screening of samples, whereas a pure culture of either H3N8 or H4N8 IAV was isolated upon testing of the corresponding duplicate sample.