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  • See this guy? He is afraid for his life. This drawing is an 1832 joke - it's a riff

  • on how nobody knew how to prevent cholera. You might suspend acorus over your masked

  • mouth, or wear a copper breastplate, and tie pitchers of water behind your calves.

  • Anything to keep the disease away. Starting in the 1830s, cholera pandemics swept

  • the United Kingdom. Nobody knew how the disease was transmitted.

  • Germs weren't an established idea. One London doctorJohn Snowtried

  • to find out how the diseases spread, and today, one of his investigations is iconic in the

  • field of epidemiology. And it all centered on a pump.

  • This is a map John Snow made to prove his solution to the cholera mystery in London.

  • It also shows the confusion and the problems he was up against.

  • Each of these bars represents a death from cholera.

  • The disease often killed half the people who got itit caused vomiting and diarrhea.

  • The rapid loss of fluids was fatal. At the time, a lot of people believed cholera

  • was transmitted in a “miasma” — imagine an evil cholera cloud.

  • This typical map from the 1840s shows a choleramistthat was blamed for transmission.

  • Snow suspected a different source. At the time, people usually didn't get water

  • directly in their homes. It came from a neighborhood pump connected

  • to one of the few water companies in the city. John Snow mapped different water company's

  • service areas in London. You can see how they are occasionally separate,

  • and occasionally overlap. If a common pump was contaminated at any point

  • at the source or near the pumpSnow believed the water could kill.

  • In 1849, he wrote that his study of symptoms and specific cases had led him to suspect

  • 'the emptying of sewers into the drinking water of the community," caused outbreaks

  • not a miasma. Five years later, he had a chance to prove

  • itand stop a fresh outbreak in the process. In August 1854, 20 people lived here at 40

  • Broad Street, including an infant who died of cholera. After her death, Snow started

  • to investigate the outbreak. He didn't think the original water source

  • was the problem, but he thought something might be wrong down the line, at the pump.

  • He took samples of the water. They seemed clean.

  • But he wasn't satisfied, because more people were getting sick.

  • He asked questions up and down the street, where one man had noticed a bad smell from

  • his water. Snow asked the registrar for a list of people

  • who'd died. He started going house by house to interview

  • the survivors - and many of the dead had taken water from the pump.

  • He became convinced the Broad Street Pump was the common link among the dead.

  • He wrote, “I had an interview with the Board of Guardians of St. James's Parish on the

  • evening of Thursday, 7th September, and represented the above circumstances to them. In consequence

  • of what I said, the handle of the pump was removed on the following day.”

  • People stopped using the water. But Snow had not won yet. Newspapers reported

  • the streets were covered in limethe city was using it as “a powerful disinfectant

  • on the streets. That showed they weren't fully convinced

  • the pump was the problem. They still suspected miasma.

  • So Snow bolstered his case through investigation and recording.

  • He learned the 18 workers who died at this factory had drunk from big barrels of water

  • drawn from the pump. At the same time, unlikely survivors could

  • serve as proof of Snow's theory. According to the miasma theory, this place

  • would've been covered in cholera clouds, affecting all workers.

  • But Snow learned the workhouse had its own wellno bad water got in.

  • The same went for this brewery. That's because Snow learned the workers

  • there drank from the brewery's water supply or, more likely, only drank the free malt

  • liquor they got on the job. That's right, drinking on the job saved

  • their lives. Snow strengthened his argument and his map.

  • He adjusted the location of the pump to show how close it was to 40 Broad Street and drew

  • a dotted line - he showed a zone where it would be closest to walk to the Broad Street

  • pump, rather than another one. That zone is where most people died.

  • He tabulated every death, by date, to do it. This was paired with a local Reverend's

  • similar data-driven investigations. A local surveyor looked at the plumbing at

  • 40 Broad Street, where the infant had died. He learned that the cesspool, where sewage

  • collected, was poorly designed and lined with decaying bricks.

  • When the infant's diapers had been washed, the cholera-carrying water had leaked into

  • the Broad Street pump's supply. John Snow died in 1858. His obituary read,

  • Dr John Snow: This well-known physician died at noon, on the 16th instant, at his

  • house in Sackville Street, from an attack of apoplexy. His researches on chloroform

  • and other anaesthetics were appreciated by the profession.”

  • At the time, Snow was more famous for stuff like a chloroform inhaler than a map.

  • It took years for theinvestigation of John Snowto become an example for subsequent

  • outbreaks and epidemiology textbooks, and it slowly, eventually, helped end the miasma

  • myth. That's because Snow didn't just make a

  • map of a city. It's a map of his process and the field

  • it shaped. It gave direction to a world where disease

  • didn't have to be hidden in a cloud. Instead, it could start at a pump.

  • OK, so the

  • best book about John Snow is Cholera, Chloroform, and the Science of Medicine. It features an

  • amazing story, which is that John Snow gave chloroform to Queen Victoria while she was

  • giving birth.

See this guy? He is afraid for his life. This drawing is an 1832 joke - it's a riff

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B1 Vox cholera pump water map john

The 1850s map that changed how we fight outbreaks

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    林宜悉 posted on 2020/08/14
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