Fig. 2

Fevers observed at the Boston-area emergency department, as compared with influenza surveillance in Massachusetts. a Fevers, weekly analysis I: weekly proportion of temperature measurements that were fevers. b Fevers, weekly analysis II: weekly number of fevers measured per thermometer. c Fevers, hourly analysis (smoothed): exponential smooth of the hourly proportion of temperature measurements that were fevers. d Fevers, daily analysis (smoothed): exponential smooth of the daily number of fevers measured per thermometer. e Surveillance of emergency departments, real time: proportion of patients with flu-like symptoms at 19 emergency departments in Massachusetts. The data are shown in blue, the seasonal trend is shown in green, and the data with the seasonal trend removed are shown in the inset. f Surveillance of sentinel providers, weekly: proportion of visits for influenza-like illness at more than 40 hospitals, private physicians’ offices, and other providers across Massachusetts that participated in the sentinel surveillance program. g Surveillance of laboratories, weekly: laboratory-confirmed cases of influenza. Periods for which data were not reported are shaded gray. In all plots, the orange bands display the CDC-defined periods of elevated influenza activity during the H1N1 (swine flu) pandemic (at left) and a seasonal flu outbreak (at right)