Key points

• 635 statistical signals detected during the 2010–2022 period corresponding to clusters of cases at the level of drinking water distribution units (DWUs) involving acute gastroenteritis with a plausible waterborne origin, including:

  • 618 signals with epidemiological characteristics particularly consistent with the hypothesis of a waterborne outbreak, including 102 since early 2019

  • 110 reports considered a priority for environmental investigations due to drinking water distribution units repeatedly implicated in multiple reports, including 21 since 2019

• 11 reports investigated, confirming an environmental origin for 8 outbreaks:

  • 73 of the investigated reports were waterborne (positive predictive value of the system)

  • The likelihood of a waterborne origin was rated as high for 3 reports (37.5%), probable for 2 (25%), and possible for 3 (37.5%) based on the classification algorithm