Fig. 3.

Combined early warnings for South Africa and the United States on the logarithm of the moving average number of cases based on cEVI, EVI, cEVI+, cEVI- for the first 700 days. cEVI- is plotted as the conjunction of EVI and cEVI. All colored dots in each panel construct cEVI+, the disjunction of EVI or cEVI. EVI alone and cEVI- construct the EVI warnings, while cEVI alone and cEVI- construct the cEVI warnings. EVI alone and cEVI alone are warnings produced only by EVI or only by cEVI, respectively. The gray dots correspond to no warnings. Primary interest lies in early identifying an epidemic within each country individually and not to compare epidemics across countries that possibly have discrepancies in reporting and diagnostic testing. Alternative versions of Fig. 3 can be found in the Appendix where the total N days are shown for each country (Figs. A1, A2).