The Broad Street Pump – Epidemiology

Resolution of the COVID crisis, that is the saving of health and lives will take several approaches. Disease in an individual is studied in a clinic and or hospital. Laboratory studies complement the data gathered in the clinic. For widespread disease study in an affected population, epidemiology is the appropriate tool.

The study of epidemiology is not unlike journalism where one attempts to weave a story around the common threads of illness in multiple individuals. It is the who, what, where, when, how of medicine. The tools of epidemiology range from good old gumshoe to powerful forensics such as DNA. Contact tracing is part of epidemiology. There is a rich history of epidemiology. Circa 400 Before the Current Era (BCE) Hippocrates noted in an essay “On Airs, Waters, and Places” that environmental and host factors may influence the course of diseases.

In the annals of epidemiology one study and one name stand out. London, England in the mid-1800s was racked by cholera outbreaks. The disease often ravaged poorer communities in flood-prone low-lying areas where fog would form. The “night air” was thought by some to be the source of cholera, called the miasma theory. John Snow, a physician thought otherwise.

He felt that it was more likely waterborne. He studied a particular outbreak in the summer of 1854. The surviving patients were in hospitals over a wide area, rather than localized. This in itself was unique. Dr. Snow with the help of Reverend Whitehead interviewed the various patients, determined where they lived, and then examined where they went on a daily basis. Essentially he took the role of a geographer to find how the paths of those impacted crossed.

Although the cholera victims lived at a distance of each other, the one commonality was their drawing drinking water from one pump – The Broad Street Pump. John Snow removed the handle from the Broad Street pump and ended the cholera epidemic. It turned out that this one well was contaminated with sewage. Cholera is waterborne. If exposure to contaminated water is stopped, the disease is stopped.

So what does epidemiology say about our current pandemic? It has revealed that our current pandemic most likely originated in a Wuhan wet market where a diverse number of different wild animals are kept for sale, even butchered on the spot. This strongly suggests and DNA studies help confirm that COVID-19 is a zoonotic, a disease formally in an animal that has “jumped” to humans. Other zoonoses include AIDS and Ebola.

Although the virus originated in Asia, the biggest outbreak, that in New York City, came through Europe on its way here. The virus is spread by droplets and/or aerosols of an infected individual which can travel several feet from just breathing but especially from sneezing or coughing. These droplets/aerosols are infectious when they contact mucus membranes of the mouth or nose.

The solution in the long term is vaccination but that is unlikely to be available until sometime next year. Until then the solution is to physically block transmission. Masks vary in their efficacy but just about any mask is better than no mask. Physical distancing works and the greater the distance the better. And wash your hands.

Dr. Bob Allen is Emeritus Professor of Chemistry, Arkansas Tech University.

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