FIG 2.

Stacked bar graphs showing total number of IAV samples collected from waterfowl per year between 1976 and 2015 in North America. (A) The number of IAV isolates recovered each year is indicated in red, and IAV-negative samples are indicated in blue. IAV isolates recovered by decade are as follows: 1976 to 1985, 2,749 (24%) IAV isolates from 11,361 waterfowl; 1986 to 1995, 304 (11%) IAV isolates from 2,721 waterfowl; 1996 to 2005, 303 (8%) IAV isolates from 3,624 waterfowl; and 2006 to 2015, 5,071 (8%) IAV isolates recovered from 60,263 waterfowl. (B) The number of samples collected each year by state or province (see key for color coding). Locations are given in descending order from north to south by latitude of the sampling site. Sampling expanded to locations throughout the extent of the Mississippi Migratory Flyway in 2006.