The number of signals, sensitivity, specificity and time to detection for C1, C2 and C3 algorithms, based on the optimal thresholds identified by employing the data for all counties.

*The low level of incidence rate ranged from 7 to 149 per 100,000, the middle level of incidence rate being 150–249 per 100,000, and the high level of incidence rate being 250–420 per 100,000.