Fig. 4
From: Detecting signals of seasonal influenza severity through age dynamics
State-level patterns of seasonal influenza severity. a State retrospective severity (\(\overline {\rho _{s, r}(\tau)}\)) may range from mild to severe in a single season regardless of the national retrospective severity index (\(\overline {\rho _{s, r}}\)). The 2007–08 (left) and 2008–09 (right) seasons, where \(\overline {\rho _{s, r}}\) values were 16 and -9 respectively, are displayed. States in white did not have sufficient data to calculate a retrospective severity index. b Deviation between state (\(\overline {\rho _{s, r}(\tau)}\)) and national retrospective severity (\(\overline {\rho _{s, r}}\)) across the eight study seasons was used to identify states that tend to experience more severe flu seasons than other states. The 75th and 70th percentiles exceeded zero for red and orange highlighted states, respectively. c Pearson’s R correlation coefficients (H o :R=0) between state early warning (\(\overline {\rho _{s, w}(\tau)}\)) and national retrospective (\(\overline {\rho _{s, r}}\)) classifications were used to suggest possible ‘sentinel’ states. Only coefficients for Illinois, Virginia, Colorado and Maine had p-values below 0.05. States in white did not have enough data to calculate at least one of the two metrics for at least one study season