In the 19th century, there was an outbreak of cholera, a waterborne disease that causes death within hours from dehydration and severe diarrhea if left untreated.
People believed that it was spread through miasma, which is bad air. However, John Snow, an anesthesiologist, discovered that it was actually spread through water.
No one believed him, despite the evidence he had.
Then, in 1842, Edwin Chadwick released a report on the dirty streets of the UK, which led to sewer systems being implanted.
After a long time and a lot of time and effort spent, the sanitary movement spread and significantly reduced waterborne diseases.
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