On March 15, 1813, John Snow was born in York, England. In 1854, Snow, a doctor, was the first person to use the geographic method to keep track of the streets where people were getting cholera, a deadly disease. Because of his map, which marked exactly where people were sick, people deduced that a contaminated water pump caused the cholera outbreak.

Snow is considered the father of epidemiology, the study of the “patterns, causes, and effects of health and disease conditions in defined populations.”

cholera
Noun

infectious, sometimes fatal disease that harms the intestines.

contaminate
Verb

to poison or make hazardous.

deduce
Verb

to reach a conclusion based on clues or evidence.

disease
Noun

harmful condition of a body part or organ.