I remember reading a story years ago where there was another legionaire outbreak in the UK. It took them ages to realize the cause was most likely people filling their windshield wiper reserves with water instead of cleaner. The water sat in the tanks and grew bacteria. The bacteria was then aerosolized every time drivers used their wipers.

I think this was around the 2008 collapse and remember it being strongly implied that people trying to save a buck may have been poisoning their own neighborhoods.

Considering how tight everyone is stretched right now, economically. I would not be surprised by an uptick of watering-down.