It was one of the deadliest diseases of the 19th century, killing tens of millions of people. And it was massively contagious. Outbreaks killed thousands of people in just days.
Problem was, no one knew what caused it. Or how it spread.
But that all changed in London, 1854. John Snow, a physician, discovered the secret behind the deadly disease in his own neighborhood.
How? By tracing symptoms to their source.
Snow lived near Broad Street. There, on August 29, a little girl died. The next day, dozens of Londoners near her home seized up with the sickness. Then a hundred the next day. One-forty-one the following day.
Something had to be done. But what? This was a choosy disease. Some family members would get it, others wouldn’t. It would strike one home and skip the next. What was the pattern? What was the source?
Snow had a hunch, and visited hundreds of the sick in London, traced what they did, and in a race against time, discovered the root cause: the Broad Street public water pump. Everyone who was sick drank water from Broad Street.
Against city opposition, He finally convinced officials to shut it down. The next day the death toll dropped to fourteen. Then nothing. Dr. Snow saved London, and ultimately, millions around the world, with a simple observation: the source of the disease named cholera was sewage-contaminated water.1
Thoreau wrote that “for every thousand hacking at the branches of evil, there is one striking at the root.” Cholera was a deadly evil. It killed millions of people because thousands of caregivers hacked the branches by treating symptoms instead of finding the root cause. But Dr. Snow struck the root. By finding the source of the disease, he dealt the death-blow to one of the deadliest diseases in human history.
It pays big to find and strike the root.
1See John Snow’s story in a recently-released documentary.