The cause of cholera — the bacterium Vibrio cholerae — was first discovered by the Italian physician Filippo Pacini in 1854, and later independently rediscovered and confirmed by the German microbiologist Robert Koch in 1883.
Filippo Pacini’s Discovery (1854)
During a cholera outbreak in Florence, Italy, in 1854, anatomist Filippo Pacini examined the intestines of cholera victims under a microscope and identified a comma‑shaped bacterium in their tissues. He published his findings in a paper titled “Microscopic observation and pathological deductions on cholera,” correctly concluding that this microorganism was the cause of the disease.
At the time, the dominant theory was that cholera spread through “bad air” (miasma theory), so Pacini’s discovery was largely ignored by the wider medical community and remained obscure for decades.
Robert Koch’s Confirmation (1883)
In 1883, during a cholera pandemic in Egypt and India, Robert Koch led a German team that isolated the same comma‑shaped bacterium from the intestines of cholera patients and from contaminated water. Koch’s rigorous work, including culturing the bacterium and linking it directly to the disease, established the germ theory of cholera and brought international recognition to the cause.
Koch’s identification of Vibrio cholerae (which he originally called Bacillus comma) finally convinced the scientific world that cholera was a waterborne bacterial infection, not an airborne “miasma”.
John Snow’s Role
Although he did not identify the bacterium itself, the English physician John Snow is famous for discovering how cholera spreads. In 1854, during a London outbreak, he mapped cases and traced the epidemic to a contaminated water pump on Broad Street, proving that cholera was transmitted through polluted drinking water.
Snow’s epidemiological work showed the mode of transmission and laid the foundation for modern public health, even though the actual germ (V. cholerae) was only confirmed decades later by Pacini and Koch.