The 19th Century: Germ Theory, Cholera, and the Public Health Revolution

The 19th century was the most important period of change in the history of medicine. Three things transformed public health: the discovery of germ theory, the cholera epidemics, and the power of government to act.

The Cholera Epidemics

Cholera struck Britain four times: 1831, 1848, 1853-54, and 1866. It killed tens of thousands each time. In 1854, the Broad Street cholera outbreak in Soho, London killed 616 people in just three weeks.

John Snow and the Broad Street Pump (1854)

John Snow was a London doctor who rejected miasma theory. He mapped every cholera death in Soho and found that they all clustered around one water pump on Broad Street. He proved that cholera was spread through contaminated water, not air. He persuaded the local council to remove the pump handle — and the outbreak ended. This was one of the most important investigations in the history of public health.

Louis Pasteur and Germ Theory (1861)

French scientist Louis Pasteur proved in 1861 that disease was caused by microscopic germs (bacteria). His Germ Theory finally replaced the Four Humours and miasma theory as an explanation for disease. German scientist Robert Koch built on this work, identifying the specific bacteria that caused tuberculosis (1882) and cholera (1883).

Edwin Chadwick and the Public Health Movement

Edwin Chadwick was a social reformer who, in his 1842 Report on the Sanitary Conditions of the Labouring Population, used statistics to prove that poor living conditions caused disease and death. He showed that the average life expectancy in Manchester was just 28 years for labourers, compared to 38 for tradespeople and 52 for gentry. The evidence was shocking.