Defining the Baseline Period for TTRB Metrics
EVENTS
When computing the TTRB, the baseline activity period for each participant was defined as any time before the latent ILI phase (ie, at least 5 days before ILI onset) or more than 21 days after ILI onset. To mitigate the potential effects of COVID-19–related SIP orders, ILI events were separated according to whether they occurred before, on, or after March 15, 2020. For the former, the baseline period was additionally restricted to before March 15, 2020, and for the latter, the baseline period was restricted to after March 15, 2020.