Video of the day -- visions of the spiritual world
Who would bathe or wash in the water of a river polluted with vast numbers of rotting corpses and the untreated sewage of a region with hundreds of millions of people? Only those for whom the physical concept of "clean" has been superseded by the spiritual concept of "pure". The Ganges river is holy and "pure" in a spiritual sense, never mind how filthy it is in reality. Small wonder that cholera has been a problem in the Ganges region for as far back as records go, and that major epidemics of the disease have started there again and again throughout history.
And don't forget that in medieval Europe, when Christianity was dominant and even the rudimentary Greco-Roman standards of hygiene had been lost, life was at least as filthy and disease-ridden as this.
This is the true face of the "spiritual".