Most Western doctors believed cholera arose from miasmas, or bad air. Others thought it was contagious and spread from person to person by touch. Neither was true. The fruitless attempts of health boards to locate the source of the disease stimulated much satire, as in the cartoon below.
The main source of cholera infection was/is water polluted by human wastes. The first person to demonstrate the water borne theory was John Snow, a London surgeon, in 1855, although the cause, the cholera vibrio microbe, was not discovered until German doctor Robert Koch isolated it in the early 1880's, and showed it could cause the disease.
Yet some people suspected the water well before Snow and Koch. In the cartoon from 1832 below, George Cruikshank indicates that some people even then pointed to the sewage-polluted Thames as the source of cholera in London. "We shall all have the cholera" one person cries, as numerous sewers empty their virulent contents into the river, the source of many people's drinking water. No wonder so many people drank gin and beer.