Mapping Cholera: A Doctor's Breakthrough

A doctor stopped a deadly cholera epidemic just by looking at a map. In 1854 London,

people were dying and everyone blamed "bad air." But Dr. John Snow mapped every single

death and discovered a terrifying pattern: nearly all the victims drank water from the same public

pump. He convinced officials to remove the pump's handle, making it unusable.

Almost immediately, the outbreak ended. He proved the disease spread through contaminated water,

not air, decades before we even discovered germs. That’s epidemiology:

playing detective with data to find the source of disease and stop it.