Nokia water supply contamination
The Nokia water supply contamination occurred from November 28 to 29, 2007, when a large part of the water supply in Nokia, Finland, was contaminated with treated sewage water. The contamination affected an area with some 12,000 inhabitants and caused an epidemic of thousands of cases of diarrhea and vomiting primarily due to Norovirus and Campylobacter infections.
Source: Wikipedia — Nokia water supply contamination (CC BY-SA 4.0)