How did John Snow’s explanation of cholera differ from the miasma theory?

During the 19th century, the prevailing medical consensus attributed cholera to the miasma theory, which posited that the disease was caused by inhaling "bad air" or noxious vapors arising from decaying organic matter, sewage, and stagnant water.12

In contrast, John Snow proposed the radical alternative that cholera was a waterborne disease caused by a germ-like agent spread through the ingestion of contaminated matter. His explanation differed fundamentally from miasma theory in the following ways:13

• Transmission Mechanism: While miasma theory focused on inhalation of atmospheric pollutants, Snow identified contaminated water as the primary vehicle for transmission.12
• Evidence-Based Investigation: Snow utilized innovative mapping and statistical analysis to link outbreaks to specific water sources, such as the Broad Street pump.
• The "Grand Experiment": Snow compared cholera mortality rates between populations served by different water companies, demonstrating that those receiving water from sewage-polluted sections of the River Thames suffered significantly higher death rates than those with cleaner water supplies.13

Although initially controversial, Snow’s work provided the critical evidence that eventually led to the acceptance of germ theory.23