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  • What if I told you that all illnesses,

  • things like the cold, the flu, strep throat,

  • came from wandering clouds of poisonous vapor?

  • You'd probably think that absurd, and, don't worry, it's completely wrong.

  • Yet that's actually what people thought caused diseases for several centuries.

  • They called it miasma theory,

  • and everyone from the public to the medical establishment accepted it.

  • But by the 1840s, in the midst of devastating cholera outbreaks in London,

  • a small group of scientists had grown skeptical.

  • Early microscopes had revealed the existence of tiny microorganisms,

  • and they proposed that it was actually these germs that cause diseases,

  • hence the name germ theory.

  • Though most people held onto their assumptions

  • and strongly resisted this theory,

  • its supporters were determined to prove them wrong

  • by collecting compelling data.

  • Leading the charge was a physician named Dr. John Snow.

  • Dr. Snow observed that cholera-infected patients

  • experienced severe vomiting and diarrhea,

  • symptoms of the gut as opposed to the lungs,

  • and thought that perhaps the disease was transmitted through food or drink,

  • not the air.

  • After investigating previous outbreaks,

  • he became convinced

  • that cholera was spread through contaminated water sources.

  • Then, late in the summer of 1854

  • when cholera suddenly struck the Soho district,

  • a neighborhood in London very close to his own,

  • Dr. Snow was hot on its trail.

  • He requested the records for the deceased,

  • and within the first week, there had already been 83 deaths.

  • He mapped out where each of the deceased had lived

  • and found that 73 of them resided close to the water pump on Broad Street.

  • Dr. Snow strongly recommended shutting down the pump,

  • and because he knew how unpopular germ theory was,

  • he suggested that cholera was spread through a poison in the water

  • instead of microorganisms,

  • when presenting his case to governmental officials.

  • They were unconvinced,

  • but agreed to shut down the pump as an extra precaution.

  • Almost immediately, new cases of infection subsided.

  • Bolstered by his success,

  • Dr. Snow was determined to connect the contaminated pump water

  • to the disease.

  • He found the story of a widow who had died of cholera

  • and lived far away from Soho,

  • but had a servant bring her water from the Broad Street pump daily

  • because she liked the taste.

  • He also discovered a workhouse

  • located around the corner from the Broad Street pump

  • that housed hundreds of people, but only a handful had become infected,

  • which Dr. Snow attributed to the fact

  • that the workhouse had its own private well.

  • Finally, Dr. Snow heard of an infant

  • who may have been one of the earliest victims of the outbreak.

  • He learned that the child's dirty diapers

  • had been thrown into a cesspool

  • right next to the public water pump on Broad Street.

  • Again, Dr. Snow presented his case,

  • but even then, city officials spurned his theory,

  • not wanting to admit that there was human waste in London's water supply,

  • or that they were wrong about miasma theory,

  • which was, after all, hundreds of years old.

  • It wasn't until 1884 that Dr. Snow's efforts

  • were vindicated by Dr. Robert Koch,

  • who isolated the cholera-causing bacterium.

  • Koch developed a technique to grow pure cultures,

  • and through a series of experiments,

  • definitively proved that a specific bacterium

  • directly cause disease.

  • Major contributions to germ theory

  • also came from prolific scientist Louis Pasteur,

  • whose study of microorganisms led to the development of the first vaccines.

  • By challenging assumptions with data-driven research,

  • these scientists discredited an age-old theory

  • and sparked a revolution that was incredibly beneficial to public health.

  • But all of this raises the question,

  • what are the widely held scientific beliefs of today

  • that our descendants will find ridiculous?

  • And as any scientist would tell you,

  • a question is an excellent place to start.

What if I told you that all illnesses,

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B2 US TED-Ed cholera dr pump theory germ

【TED-Ed】How a few scientists transformed the way we think about disease - Tien Nguyen

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    Ann posted on 2015/11/21
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