Medieval Diseases


Encyclopedia Americana. Various entries.

The Dictionary of the Middle Ages. “Black Death” and “Plagues, European,” by Robert S. Gottfried. “Leprosy,” by Stephen R. Ell. Edited by Joseph R. Strayer. New York: Scribners, 1982.

Back to Medieval Matters

Life before the discovery of penicillin, antisepsis, and germ theory necessarily meant that disease was a constant companion of medieval people. Fortunately, from the eighth through the mid-fourteenth centuries Europe was remarkably free from most epidemic diseases. There were still plenty of endemic diseases and poor health conditions related to famine and malnutrition. But these centuries of thriving allowed Europe’s population to grow to an estimated 75-80 million, to expand in every direction, to build densely-inhabited cities, and to establish trade routes with all parts of the known world, setting the scene for a new pattern of epidemic disease across Europe and Asia.Following are some of the important infectious diseases in Europe during the late fourteenth century. Some were epidemic; some endemic. Nearly all fell harder on the very young, the very old, and those whose resistance was weakened by poor diet, hard labor, or previous disease. Medieval physicians would have treated these illnesses one symptom at a time, with separate prescriptions for fever, cough, chills, and so forth.

Dysentery (the “bloody flux”)

An infection caused either by bacteria or amoebas, spread through contamination of food and water by infected fecal matter.

Symptoms: (Bacillary) After 1-6 days incubation, watery stools, fever, cramps, dehydration. In advanced stages, bloody stools, meningitis, conjunctivitis, and arthritis. (Amebic) Acute form: watery, bloody stools, cramps, fever, weakness. Chronic form: intermittent diarrhea, mild abdominal discomfort.

Result: Generally weakened condition.

Note: Endemic in medieval armies and pretty common in cities. Infantile diarrhea was a leading cause of death for infants. After the Black Death, many urban areas instituted public health reforms to improve sanitation and prevent these enteric fevers.

Ergotism (“St. Anthony’s fire,” “holy fire,” “evil fire,” “devil’s fire,” “saints’ fire”)

Poisoning from a fungal infection of grain, especially rye.

Symptoms: (Convulsive) Degeneration of the nervous system causes anxiety, vertigo, aural/visual hallucinations, and the sensation of being bitten or burned; stupor, convulsions, and psychosis. (Gangrenous) Constriction of the blood vessels causes reddening and blistering of skin, then blackening, with itching and burning, and finally necrosis.

Result: 40% mortality. Lingering symptoms, including mental impairment, among survivors.

Note: Ergotism was known as a rural disease, particularly of marshy areas, and one that followed crop damage or famine; especially after a severe winter and a rainy spring. Children are more susceptible because of their smaller body weight. Because England did not rely on rye as much as populations on the continent, it suffered fewer cases of the convulsive type.


A bacterial infection of the genital tract, transmitted through sexual contact.

Symptoms: (Male) After 2-8 days incubation, urgency and burning sensation on urination, profuse discharge of pus. Inflammation of prostate and seminal vesicles may lead to fever and urinary retention. (Female) After 2-8 days incubation, mild urethritis; or may be entirely asymptomatic. If infection spreads to the upper tract, acute fever and abdominal pain. Bacteria may invade the bloodstream and produce infections in other parts of the body, most commonly arthritis; the sufferer develops fever and hot, swollen, painful joints.

Results: In males, symptoms subside in several weeks; in females, a month or two. Serious infections may result in infertility for both males and females.

Note: Sufferers may remain infectious for months following an attack. Not a nice disease.


An acute, extremely contagious viral infection of the upper respiratory tract, spread by inhalation.

Symptoms: After 1-2 days, a sudden onset of chills and fever, headache, backache, muscular aches, and general malaise; weakness, prostration, nausea, eye pain, mental confusion. After 1-5 days the respiratory symptoms become more prominent: dry or sore throat, cough, runny nose. Serious complications include bronchitis and bacterial pneumonia.

Results: A few months, maximum, of resistance to repeated infection.

Note: Flu was not a major worry in the 14th century but became a scourge in the 15th. Because flu is very contagious it often forms epidemics, generally occurring in the winter or early spring.

Leprosy (“lepry”)

A bacterial infection, transmitted by respiration or contact, leading to disfigurement.

Symptoms: After a variable but possibly years-long period of latency, facial features begin to coarsen and the voice becomes hoarse. Eruptions of the skin and eyes begin as pale spots that turn into red, raised, firm nodules. Skin spots are insensitive to cold, touch, and pain; hands and feet lose feeling and eventually muscle weakness and paralysis set in, usually in the face and hands. Secondary infections of lesions or unnoticed wounds become gangrenous. Blindness often occurs. The nose decays. The hands and feet become clawed.

Results: Eventual, ugly, lingering, friendless death, sometimes taking over 20 years.

Note: Most people are immune. Individual resistance causes much variation in the form and pace of the disease. The disease may have assumed its worst form among the upper classes, as the organism requires cholesterol as a growth factor. Lepers were forbidden to mingle with the unafflicted; their religious, legal, and social status was complex.

Malaria (“the ague”)

A parasitic disease spread by mosquitoes.

Symptoms: Shaking chills, then fever to 104 degrees, severe headache. After several hours the sufferer begins sweating profusely; then the headache and fever disappear. Attacks recur every 48 hours (a “tertian” fever) or 72 hours (a “quartan” fever). Weakness, some anemia.

Results: Survivable. Limited immunity.

Notes: Chronic in southern and low-lying areas of Europe, including southern and eastern England. The name “malaria” comes from the Italian for “bad air,” which was believed to cause the disease before the agency of mosquitoes was understood. The only type of malaria that occurs in England is rarely fatal.


A mild, highly contagious viral disease transmitted via respiration.

Symptoms: After 7-14 days, coldlike symptoms develop (runny nose, dry cough, fever to 105 degrees, aching), plus inflamed and sensitive eyes. Around the third day, bright red spots appear inside the mouth. Day four: characteristic red rash; slightly raised and mildly itchy; starts on face and spreads over the rest of the body. Fever and rash begin to depart after a few more days.

Results: Survivable; complications can include blindness and heart or brain damage. Survivors have complete immunity.

Notes: Occurs mostly in late winter and early spring. The disease is so ancient in Europe that humans tend to survive it. Primarily a childhood disease (since most adults had been exposed to it), but infants younger than 6 months have a temporary immunity from their mother.


A bacterial infection, transmitted by flea bites (or secondarily by respiration), that takes several different forms.

Symptoms: (Bubonic): After 2-6 days, necrosis of the flea bite and heat and swelling in the nearest lymph nodes (neck, groin, or armpit); buboes can be as large as an orange and extremely painful. Headache, fever, delirium. 20% go on to develop the pneumonic form. (Pneumonic) less common but more infectious: A lung infection, with coughing and sneezing. (Septicemic) rare: Infection spreads throughout body in the bloodstream; death occurs too fast (within hours) for buboes to form.

Results: Bubonic form: 50% to 70% mortality; other forms:100% mortality. No immunity.

Notes: The horror of plague was in not only its virulence but the frequency of its recurrence. After the 1347-51 European pandemic, which killed 25-40% of Europe’s population, further attacks struck England in 1361-62 (the “Children’s Plague,” killing 20% of the population of England, primarily the young), 1369 (10-15% of the population), 1375, 1379 (north country), 1381-82 (midlands), 1383 and 1387 (southeast), 1390 and 1399-1400 (over 10% of the national population), 1405-6 (national), 1410-11 (Wales and the west country), 1411-12 and 1413-14 (national), 1420 (East Anglia), 1423 (national), 1426 (London), and 1428-29 (national). It took Europe until the 19th century to recover its early 14th-century population levels.

Puerperal fever (“childbed fever”)

A bacterial infection of the female reproductive organs following childbirth.

Symptoms: Chills, high fever, abdominal pain, nausea; possible spread of infection to rest of body.

Results: Chances of mortality depend on what kind of bacteria caused the infection; it can be nearly anything. Tetanus or gas gangrene are especially bad bets. Possible infertility in survivors.

Notes: Susceptibility to infection is increased by prolonged labor in childbirth, rupture or retention of the placenta, and other unfortunate occurrences.

Smallpox (the “red plague”)

A severe, highly contagious viral disease transmitted by inhalation.

Symptoms: After 12 days incubation, high fever, chills, severe headache and backache, and general malaise. Hemorrhages may occur in lungs or other organs. After 4 more days a distinctive itchy rash of red lesions appears on face, arms, legs, and sometimes the trunk. The bumps become pus-filled blisters; if secondary infections do not occur, they break and begin to dry up in about 9 days.

Results: Mortality 25-30% for the severe form; 1% for the mild form. Survivors have distinctive pitted scars and complete immunity to further infection.

Notes: Varies in severity from a mild form with few skin lesions to a highly fatal hemorrhagic form. The majority of deaths occur in the second week of the disease. It was a horror in the 15th century; during the 1440s in France smallpox may have killed more people than plague. (It came to be known as “smallpox” later, to distinguish it from the “great pox,” syphilis.) It became primarily a childhood disease, since most adults had already been exposed.

Typhoid fever

Bacillary infection transmitted via feces.

Symptoms: Diarrhea, abdominal pain, fever to 105 degrees, blinding headache, cough, exhaustion. Patches of red on the abdomen. Symptoms can last for weeks. Complications include pneumonia, intestinal hemorrhage, and coma.

Results: 10-20% mortality.

Notes: Another of the enteric diseases.

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