Cholera is an infectious disease that spreads due to polluted water via the face-oral route. According to , the disease was thought to have been imported from Europe in 1849 by Irish immigrants who were escaping the potato famine. The then-dominant ”miasma hypothesis” attributed the cause of cholera to toxic air. However, the germ hypothesis of disease gained more popularity in the 1850s. A discovery made in 1857 by the London physician John Snow altered the prevailing perception regarding the spread of cholera. Using observational data and a ”Ghost Map,” Dr. Snow connected the deaths due to the cholera outbreak that devastated London during 1854 to a sewage-contaminated water pump that supplied water to houses.