The period spanning the 5th to the 15th centuries in Europe was defined by high mortality rates due to disease. Lacking modern scientific understanding, illness was often attributed to divine judgment or astrological forces rather than biological causes. Poor hygiene, close quarters in urban centers, and reliance on contaminated water sources created an environment where infectious diseases flourished. The prevalence of illness profoundly shaped Medieval society, influencing demographics, economics, and daily practices.
The Cataclysmic Epidemics
The Black Death, the most devastating disease event in European history, first swept across the continent between 1347 and 1353. This pandemic was caused by the bacterium Yersinia pestis, which spread from Central Asia along trade routes via infected fleas carried by rats. Close living conditions and lack of sanitation in Medieval towns facilitated the rapid spread of the disease.
The infection manifested in three main forms, each with distinctive symptoms. The most common was the bubonic plague, characterized by fever, chills, and the painful swelling of lymph nodes, known as buboes. The pneumonic form was rapidly fatal, affecting the lungs and allowing for human-to-human transmission through respiratory droplets. Septicemic plague, the rarest but almost universally fatal form, occurred when the bacteria entered the bloodstream directly, leading to internal bleeding. The Black Death was catastrophic, wiping out an estimated 30 to 60 percent of Europe’s population and causing massive demographic collapse.
Endemic and Chronic Afflictions
Medieval communities were constantly burdened by chronic and long-term illnesses that were endemic to the population. Leprosy, or Hansen’s disease, caused by the bacterium Mycobacterium leprae, was widely feared for its disfiguring effects on the skin, nerves, and extremities. Those afflicted were subjected to severe social isolation, forced to live in dedicated communities known as lazar houses and ringing bells to warn others of their presence.
Tuberculosis, commonly called Consumption or phthisis, was another pervasive killer, particularly in densely populated areas. Caused by Mycobacterium tuberculosis, the disease slowly ravaged the lungs and other organs, leading to a wasting away of the body. Evidence suggests that its co-infection with leprosy may have contributed to the mysterious decline of leprosy cases in the later Middle Ages. Endemic diseases like Smallpox and Measles were constant threats, frequently acting as deadly childhood diseases that kept overall life expectancy low.
Maladies of Sanitation and Diet
Many common ailments resulted directly from environmental conditions, including poor public health infrastructure and inadequate nutrition. Dysentery, often referred to as “the bloody flux,” was rampant, caused by bacterial or parasitic infections transmitted through water and food contaminated by human waste. The disposal of sewage and refuse directly into streets and water sources was a primary driver of these gastrointestinal diseases.
Typhoid fever, another waterborne illness, was common in urban settings where human and animal waste polluted the environment. Reliance on grain, especially rye, as a dietary staple led to outbreaks of Ergotism, nicknamed St. Anthony’s Fire. This poisoning was caused by ingesting grain contaminated with the fungus Claviceps purpurea, which produces powerful alkaloids. Ergotism presented in two forms: gangrenous ergotism, which caused a burning sensation followed by the loss of limbs due to restricted blood flow, and convulsive ergotism, which resulted in seizures, hallucinations, and psychosis.
Medieval Medical Responses
The prevailing medical framework used to diagnose and treat illnesses was the Theory of Humors, inherited from the ancient Greek physicians Hippocrates and Galen. This theory posited that the human body was composed of four primary fluids—blood, phlegm, yellow bile, and black bile—and that health depended on the balance of these humors. Sickness was interpreted as an imbalance or excess of these bodily fluids, dictating the course of treatment.
Treatments aimed at restoring this humoral balance through various methods of evacuation. Bloodletting, performed by physicians or barber-surgeons using lancets or leeches, was a common practice intended to remove excess blood. Purging and enemas were also employed to expel unwanted bile or phlegm from the body, often using herbal concoctions. In response to the Black Death, public officials implemented early public health measures, most notably the system of quarantine, where ships and people were isolated for a set period to prevent the spread of contagious disease.