A substantial minority of the efforts in this
space test some kind of forecasting method. (Note that many
papers use the term predict, and some even misuse forecast, to
indicate nowcasting.) In addition to forecasting models that
incorporate disease dynamics (recall that these are out of scope
for the current paper), two basic classes of forecasting exist: lag
analysis, where the internet data are simply time-shifted in
order to capture leading signals, and statistical forecast models
such as linear regression.