Differences in ILI Burden and TTRB Between Participant Cohorts
infection
REGRESSION, INFECTION, FLU, INFLUENZA
The day-by-day deviations from typical healthy behavior, cumulative ILI burden, and TTRB were compared between the participants who did and did not seek health care as well as between those with confirmed influenza infection and those with ILI symptoms only.Differences between the cohorts in the day-by-day residuals were assessed using linear mixed-effects regression. The dependent measures were day-level residuals from days −4 to +9 and an additional measurement for baseline, which was the mean residual across healthy days. The model included a categorical fixed effect for ILI day (15 levels, one for each day from days −4 to +9 and an intercept for baseline) and a categorical fixed effect for cohort membership (health care seeker vs nonseeker for one model and confirmed influenza vs ILI symptoms only for the other model). A random intercept was specified on the participant ID. This model was repeated 10 times, once for each combination of the 5 activity features and 2 cohort comparisons. A total of 14 pairwise contrasts were computed per model; each compared the change in residuals from baseline between the 2 cohorts (ie, cohort 1 [flu day − baseline] − cohort 2 [flu day − baseline]). Differences between the cohorts in the cumulative ILI burden were assessed using Welch 2-sample Differences between the cohorts in the TTRB were calculated using the Mann-Whitney 