Table 2. GrippeNet.fr (GN) incidence computation criteria, France.

Computation criteria		Aim	Description
Raw criteria		Basic computation on raw data	All ILI/ARI episodes are considered. Weekly incidence rate is computed as the number of ILI/ARI episodes in the week divided by the total number of GN participants in the cohort from the beginning of the season up to that week
Episode reporting criteria	First survey exclusion	To account for first-time reporting bias	Weekly incidence rate is computed in the same way as for the raw criteria, but with the exclusion of the first report of each new participant
	Episode merging	To exclude reports on clinically unlikely different episodes	As raw, with the merging of consecutive ILI/ARI episodes within 2 weeks of each other
Participation criteria	Minimum number of symptoms reports (m)	To exclude individuals who have reported rarely	Denominator in the incidence computation is equal to the number of participants who filled ≥ m reports, m = 2, 3
	Participation window	To discard irregular participation and define a time window during which a participant can be considered actively engaged in the study	Denominator in the incidence computation is equal to the number of participants who reported at least once in the time window of n weeks before and after the reporting week; n = 0, 1, 2, 3, 4 (n = 0 means that participants are counted only in the week of reporting; n = 1 means that participants are counted in the week of reporting and also in the week before and in the week after)

ARI: acute respiratory infection; ILI: influenza-like-illness.