How did cholera spread through drinking water according to Robert Koch's investigations?

During his investigations in India, Robert Koch identified the comma-shaped bacterium responsible for cholera and confirmed its transmission through contaminated drinking water, as well as through food and clothing.1

While Koch is credited with isolating the bacterium and describing its role in the disease, his observations regarding waterborne transmission were not entirely original. The primary mode of transmission via contaminated water had been previously described by the British physician John Snow in 1849. Koch’s work was instrumental in providing the bacteriological evidence that helped move the scientific community away from prevailing theories, such as miasmatism, which incorrectly suggested that cholera was spread through contaminated air.2

Today, it is understood that cholera spreads via the fecal-oral route, where water contaminated with feces containing the bacterium is ingested by individuals.3