Snow Story

The Cholera Detective

People in England waited fearfully as cholera spread across Europe in the 19th century. By 1954 the disease was killing people in London. No one knew what caused the disease so what could anyone do to avoid it? Many people believed in miasma--that disease was caused by breathing bad air. Others thought cholera killed people who had impure bodies. There was even the idea that cholera came from eating rotten fruit or from getting too angry. Dr. John Snow thought differently. He thought cholera was spread by something in water. But no one believed him.

On August 31, 1854, a major outbreak occurred in Soho, the part of London where Dr. Snow lived. In three days, 127 people near Broad Street died. Dr. Snow talked to families of those who had died and found that nearly all the deaths were of people who drank from the Broad Street well. Families who got their water from a different pump had suffered only 10 deaths and most of these were children who sometimes drank from the Broad Street pump. He also found out that none of the workers in the nearby Broad Street brewery contracted cholera. As they were given a daily allowance of beer, they did not consume water from the nearby well.

Snow took a sample of the water from the pump and looked at it under a microscope. He saw white flecks in the water and decided these were the cause of the disease. Although they still weren’t sure, the local officials decided to follow Snow’s advice and removed the handle from the pump so no one could get water from that well. Except for a few cases, the disease in the Soho area stopped. Snow continued to be a detective and followed up on the other cases. He discovered that a woman who now lived far away from the Broad Street pump had once lived near it. She liked the taste of its water so much that she got a large bottle of it each day. That water led to her death.

Another person, Reverend Henry Whitehead, helped prove Snow’s theory. He found out that a young child living on Broad Street had been sick with cholera and the diapers had been washed in a tub of water that was thrown into a cesspool that was just three feet from the pump. The cholera bacteria had moved underground into the water supply.

Snow went on to study the water contents from homes supplied by different water companies in other parts of London. He concluded that it was indeed impure water from the big companies that allowed the spread of cholera to progress rapidly. He went on to prove his theory through the observation of prisons in London, finding that cholera cases ceased in these places only a few days after switching to cleaner water sources.