John Snow

Medical Meanderings 18 July 2007

Water From The Well

And I would have stayed up with you all night / Had I known how to save a life…
The Fray, “How To Save A Life”

London, England, in the 1850s, was a rather miserable place to live on a good day, and positively deadly at less fortunate times. In a world of no sewers, no water purification plants, no germ theory and no antibiotics, the “terrorist” most feared was cholera. Cholera is an infectious disease rarely encountered in modern America, but it remains the most common cause of death for children in the developing world, and over 60 countries have outbreaks each year.

The first known epidemic of cholera occurred in 1817 in India, but like West Nile virus in our time, it quickly spread around the world, reaching England in 1831. In 1853, with approximately 1.5 million people living in London, cholera killed 10,675. (To give you perspective, this death rate would be the equivalent of a bioterrorism attack killing 16,000 people in present-day Denver.) In late August 1854, a woman dumped a pail of water in which she’d been washing her ill infant’s diapers. The wash water, carrying cholera bacteria, percolated through the broken brick lining of the Broad Street water well.

The Broad Street well was a popular source of clear drinking water for a neighborhood of 25,000 people living packed together at 300 persons per acre. But clear doesn’t mean clean. From August 31st to September 9th, 700 people died of cholera from drinking Broad Street water. Entire families died together in one room, and only a rare family survived without losing at least one member. It was the most concentrated loss of life from cholera in English history.

Adding to the terror of the epidemic was the fact that no one in the 1850s knew about germs. The best scientific minds thought that cholera was transmitted by “miasma,” or bad, stinky air. There was plenty of stinky air in a big city with horses, cattle and humans sharing crowded living conditions with no sewer system. Miasma theory had a strong hold on the medical establishment for centuries, and like pseudoscience today, it was advanced by strong opinions based on no facts.

That all changed when a general practitioner named John Snow looked at the problem. Snow--a 34 year old expert in the use of the anesthetic ether--had already published a study in 1849 arguing that cholera was not caused by bad air, but by contaminated water. His idea was not noticed. But during the 1854 outbreak, by doing the hard medical detective work now known as epidemiology, Snow concluded that the pump was the source of the outbreak. He had the pump handle removed, saving untold lives. Incredibly, Snow never knew about the existence of the cholera bacterium. He solved the mystery just by observation, and put the dangerous nonsense of miasma to rest.

Next time you flush your toilet or get a drink of water from your tap, take a moment to think of John Snow and be grateful that, because of his work, your toilet water won’t end up in your glass.