Which two people interviewed residents and studied patterns of the cholera outbreak in London in 1845, creating a dot map that showed clusters around the Broad Street Pump?

• A. John Snow and Henry Whitehead
• B. John Snow and Louis Pasteur
• C. Henry Whitehead and Edward Jenner
• D. John Snow and Robert Koch

Answer: (A)

This item tests how early epidemiologists used data collection and geographic patterns to identify a disease source. John Snow, a physician, and Henry Whitehead, a local clergyman who spoke with residents, gathered firsthand accounts and mapped where cholera cases appeared. Their dot map revealed a concentrated cluster of cases around the Broad Street pump, pointing to contaminated water as the likely source. When the pump handle was eventually removed, cases fell, providing strong support for a waterborne transmission rather than an airborne or “miasma” theory. The other figures listed contributed to germ theory and vaccination in different ways, but they did not perform this combination of resident interviews and spatial mapping to locate the outbreak source.