FIGURE 2.
Respiratory hospitalization incidence explained by influenza-like illness incidence versus influenza virus subtype counts and reports of drift variants: the Netherlands, 1999–2005.
Note. The hospitalization incidence for individuals aged 65 years or older is plotted in a line graph with the predicted value and the 95% upper limit (Appendix B, available as an online supplement at http://www.ajph.org). Values exceeding the model's upper limit are indicated by the ellipse. Below the line graphs, the counts of influenza isolates by subtype—A(H3), A(H1), and B—are presented as bars on the x-axis, and reports of drift variants are indicated. aBecause we used generalized estimating equation models, confidence intervals for prediction were not available.