in the first cholera epidemic none of the treatment methods he had learned were working = his patients died.
kept journals with his observations and theories.
second cholera epidemic - believed cholera was a communicable disease, transferred from one man to another. It affected all classes because it transmitted through water (he needed more proof)
plotted every death on a map and after collecting data about the water supply, most of the deaths came from the same water pipe - people drinking from different wells were healthy.
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