Figure 4.

For each case definition (Table 1), the odds ratio for susceptibility to symptomatic disease for persons aged ≤17 versus ≥18 years during an April–May 2009 outbreak in Washington State, United States. The labeled short horizontal lines denote the point estimate, and the solid vertical lines capped with symbols (hollow diamond) denote the 95% confidence intervals. The solid gray horizontal line denotes a null odds ratio of 1.0.