NorthernLad

That which does not kill us makes us stronger.

MacScot

...probably some truth in that...an evolutionary advantage in making us stronger. We are, afterall, the descendents of those people that lived in the middle ages and earlier. They rarely washed their bodies let alone their hands and soap was almost non-existent.

The faecal-oral route of bacterial contamination and consequential mild to moderate gastro-intestinal upsets was rampant then...but not fatal...so an immunity must have developed.