What is the worst water infection ..??

Cholera: Although there have been no cases in England for a hundred years. An easily treatable pathogen in water Giardia, a protozoa like the amoeba can cause a wide range of symptoms including protracted diarrhea. There are other bacteria and protozoa in contaminated water such as Campylobacter, Salmonella, Shigella, E.Coli and other organisms besides. Clean drinking water is a health priority.

Waterborne illness: The one that sounds the scariest has to be Naegleria fowleri (or the brain-eating amoeba). However, I think the earlier response is probably on target - Cholera - because it can cause devastation to so many.

Depends: There are many bad infections that spread through water and can kill. In addition to cholera and amoeba, typhoid and other salmonellae, shigella, enterotoxigenic E coli, hepatitis A and E, and many more. Worst is the one that makes you sick or kills you. Wish you good health!