A winter season is composed of 3 subperiods defined as follows: an epidemic period is a 5-week period centered around the week with the highest acute gastroenteritis (AGE) incidence, a pre-epidemic period is the 100 days before the AGE epidemic period, and a postepidemic period is the 100 days after the AGE epidemic period. These periods were defined according to data collected by the French Sentinelles network. Points on the timelines are defined as follows: C refers to the week of AGE winter epidemic peak, B refers to point C minus 2 weeks; D refers to point C plus 2 weeks, A refers to point B minus 100 days, and E refers to point D plus 100 days. PPI indicates proton pump inhibitor.