<figure>
 <img src="https://media.eaglewebservices.com/public/2019/8/1565966623908.jpeg" alt="Richard P. Holm, MD" />
 <figcaption>Richard P. Holm, MD</figcaption>
 </figure>It was in London, England, 1854, when a severe diarrhea illness caused the deaths of 500 adults and children over a ten-day period and proved the value of scientific thinking.&nbsp;Physician-scientist John Snow mapped out the locations of those sick, and his work pointed to water from a hand pump well on Broad Street as a possible cause of the illness. He persuaded authorities to shut down the source by removing the pump handle from that well. Shortly thereafter, deaths from the illness abruptly slowed and scientists became convinced of the danger of this contaminated water.Over the next years, scientists identified Vibrio cholerae bacteria as the cause of that illness in London. The original pump is still there on what is now Broadwick Street, commemorating what is thought to be the founding event in the history of epidemiology, the science of understanding epidemics, infections, and patterns of illnesses in populations.The word cholera comes from the Greek word which means “yellow bile,” from an ancient and misinformed idea that all illnesses are from an imbalance of yellow bile, phlegm, black bile or blood. We know today there are many causes for infectious diarrhea including viral, bacterial, and parasitic. In the mid-1800s with the aid of the newly discovered microscope, we came to realize how to categorize bacteria, and that cholera was likely responsible for many of the pandemics throughout history. Sadly, despite all our present accumulated knowledge, human diarrhea from cholera persists today in developing countries, mostly the result of polluted water.<figure>
 <img src="https://media.eaglewebservices.com/public/2019/12/1576508816063.png" alt="" />
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 </figure>Cholera can kill within hours if left untreated. It causes severe vomiting along with three to five gallons of “rice-water” diarrhea per day resulting in severe dehydration. Unfortunately, highly infectious fecal material can too easily get into the water supply spreading the infection, especially to the very young, old and immunocompromised. More challenging is that 75 percent of people infected with cholera may not have symptoms but can still carry and spread the infection for two weeks after exposure.&nbsp;Boiling all water before drinking would prevent the spread of all water-born illnesses. Rehydration and antibiotics are initial interventional therapy for cholera. However, too often, these preventions and treatments are not easily available in developing countries. The World Health Organization, an arm of the United Nations, estimates that, each year, three to five million cases of diarrhea and more than 130,000 deaths are still due to cholera.The science of epidemiology began by discovering the water-source of a dangerous diarrhea illness and we learned how, by simply removing a pump handle, we could prevent illness.&nbsp;Richard P. Holm, MD is founder of The Prairie Doc® and author of “Life’s Final Season, A Guide for Aging and Dying with Grace” available on Amazon. For free and easy access to the entire Prairie Doc® library, visit <a href="http://www.prairiedoc.org">www.prairiedoc.org</a> and follow Prairie Doc® on Facebook, featuring On Call with the Prairie Doc® a medical Q&amp;A show streamed most Thursdays at 7 p.m. central. &nbsp;

Prairie Doc Perspectives: Science of understanding epidemics