Happy Birthday, Epidemiology!
There was a time not so very long ago in human history when we believed that miasmas (bad air) caused illness. Doctors didn’t even wash their hands between seeing patients because how could gentlemen be responsible for spreading illness?
A doctor during the Black Death protecting himself from the miasma causing the plague (or from flea bites and airborne Yersinia pestis)
There were no microscopes, so no one could look and see bacteria doing battle with our own immune system. People could only know what they observed and what they observed was that the areas where disease was most prevalent were also very smelly from the dead and dying people. It makes sense that they would infer the smells they observed to accompany sickness and death were what was causing the illnesses.
We know now, of course, that the smell so common in areas where poor people lived wasn’t the cause of their illness, but another product of the things making them sick. Bodies and human waste (read: lots of poo) left in the streets, rotting food, animals and humans living in close proximity, and sewage in the water are all very smelly and cause a host of human illnesses. Germ Theory tells us that these things become the breeding grounds of virus, bacteria, fungi, and other tiny critters which make us sick. By eliminating those risks from our environment, we eliminate a lot of the pathways those germs take to making us ill.
Cholera Outbreak of 1854
London of 1854 was a place of tremendous wealth as well as bonebreaking poverty. Illness was common and living conditions for many in the city were very poor. Sanitation in London’s poorest areas was also very low quality and it was easy for sewage and the local well water to mix—including sewage contaminated with waste from others who had cholera.
Cholera is a terrible disease. It’s caused by a bacteria called vibrio cholerae and manifests as horrific diarrhoea which kills quickly and spread like wildfire through communities. At the end of August in 1854, water from a cesspit (the place where the poo and other human waste is intended to go) seeped into the water being run to the Broad Street Pump in Soho. Over 3 days, 127 people died and the community was fleeing in the hope of staying alive (if they were able). By the 10th of September, more than 500 people had died and it was clear the outbreak had to be stopped. Dr. John Snow theorised that miasmas weren’t causing the cholera and (with the help of a local reverend) began interviewing the people remaining in the community.
Dr. Snow’s map of cholera cases in the 1854 epidemic
After his household survey, Dr. Snow realised the cases of cholera were concentrated around the Broad Street Pump. Epidemiologists like to tell a version of the story which has him marching over to the pump and pulling off the handle himself, but my Historian Heart requires to narrate that he worked with local officials to remove it.
Regardless of whether or not he removed the handle himself in a fit of epidemiological power, removing the handle ended the epidemic. In all, just over 600 people died, but the point was made that sometimes simple solutions are just what we need to save lives. Thankfully, today there is an effective vaccine for cholera and oral rehydration solution is an effective treatment to help those who become sick.
So what do epidemiologists do now?
Lots of things! Epidemiology is the study of human health and disease (epi is ‘among’ and demos is ‘people’) and we do exactly that. Epidemiologists investigate communicable disease outbreaks, track trends in interpersonal injuries (I work a lot on understanding emergency department visits for sexual assault), and monitor the health effects of environmental risks. We do it all!
Our methods in some cases are a lot more sophisticated (like in syndromic surveillance), but I’ve done lots of household surveying which involved going door-to-door asking questions and mapping the responses I received. The type of epidemiology I practice has historically excluded indigenous ways of knowing, but I’m proud that’s changing and there’s more emphasis on data sharing and partnerships with native communities.
I love the work that I get to do and I’m grateful to Dr. John Snow for launching epidemiology as a field separate from pure medicine and rooted in working with communities to find the “pump handles” which we can use to improve our own health.
