1849: In 1848 the second cholera epidemic arrived in London
and was thought to be because of “miasma” or “bad air”.
John Snow had first hand experience of the disease from 1832
and could directly exclude the hypothesis of "bad air" and went on to
hypothesize that cholera was attributable to a self-replicating
agent which was excreted in the cholera evacuations
and inadvertently ingested, often through water.
He could later test his hypothesis in 1854 when another outbreak occurred. (1 jan 1848 ano – 1 jan 1854 ano)