"the physician John Snow (1813-1858) made a major contribution to fighting cholera when he was able to demonstrate a link between cholera and the contaminated drinking water through his pioneering studies"

source: https://www.rcseng.ac.uk/library-and-publications/library/blog/mapping-disease-john-snow-and-cholera/#:~:text=But%20it%20was%20not%20until,York%20on%2015%20March%201813.