Epidemiology Practice Test

The key idea is recognizing who first connected a disease outbreak to an environmental exposure and used data to guide action. John Snow did just that during a cholera outbreak in London in 1854. He collected cases, mapped where they occurred, and compared people who drank from different water sources. He found a strong concentration of cases around the Broad Street water pump, suggesting the water supply was the source rather than some airborne illness. By removing the pump handle, the number of new cases fell, which provided practical evidence that cholera was spread via contaminated water. This combination of data collection, spatial analysis, and a public health intervention embodies the approach of modern epidemiology, earning Snow the title. The other figures contributed in important areas— Jenner with vaccination, Lind with early clinical trials, and Louis with evidence-based medicine—but they did not link cholera specifically to water sources.