alt Hacker NewsThat seems a bit silly thinking they are not doing anything to protect the water supplies, and even more silly to not compare the impact of the things you are comparing. Poison a water supply and you hit how many, a city, a small part of a city? Now compare it to the impact of a virus like corona - we literally just went through that..
Instead of poisoning the water supply, you'd stuxnet the pumps. I imagine the network interfaces for status and control are about as well protected as grocery store freezers.
A bad pathogen could go world wide, but you could trash multiple cities with online attacks. No electricity, no water, no communications. Things would get bad.