Table 2.

Mean Monthly Prevalence of Avian Influenza Virus and Stages of the Annual Cycle for Dabbling Ducks in Alaska and California

	Alaska			California
Host species	August	September	October	November	December	January
American wigeon	0 (1:5.0)	3.0 (1:5.9)	11.0 (1:2.1)	7.1 (1:3.2)	0.3 (1:1.3)	0.6 (1:0.3)
American green-winged teal	4.8 (1:0.9)	15.3 (1:4.8)	3.0 (1:1)	2.7 (1:0.4)	1.4 (1:0.6)	1.1 (1:0.3)
Mallard	9.1 (1:0.5)	23.9 (1:2.1)	4.1 (1:0.2)	3.1 (1:0.4)	1.5 (1:1.8)	0.4 (1:1.1)
Northern pintail	6.6 (1:1.7)	15.0 (1:3.5)	3.2 (1:0.9)	4.0 (1:0.9)	0.4 (0:0.1)	0.7 (1:0.2)
Northern shoveler	—	32.2 (1:7.0)	6.4 (1:3.0)	4.9 (1:1.6)	6.2 (1:1.3)	1.0 (1:0.6)
Mean monthly prevalence	4.1 (1:1.1)	17.9 (1:3.8)	5.6 (1:0.9)	4.4 (1:0.9)	2.0 (1:1.1)	0.8 (1:0.5)
Premigration staging
Fall migration
Overwintering

The ratio of after hatch-year to hatch-year birds sampled is shown in parentheses. The highest monthly prevalence of AIV and ratio of hatch-year birds are highlighted in bold.