The cholera outbreak investigated by Snow and Whitehead occurred in which city?

• A. London
• B. Paris
• C. New York
• D. Cairo

Answer: (A)

The main idea here is how early epidemiologists identify disease transmission routes through careful data collection and a natural experiment. John Snow’s investigation of a cholera outbreak took place in London, where he mapped cases and traced many to people drinking water from the Broad Street pump in Soho. By removing the pump handle, he interrupted transmission and saw cases decline, supporting the idea that cholera was spread via contaminated water rather than by miasma. This London study is the classic example being cited, so the city is London, not Paris, New York, or Cairo.