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A Historical Microbiology Lesson: Pathogens and Infectious Diseases of Medieval Times in Europe

Kitty is a registered nurse. She uses what she has learned on the job to inspire and encourage others to take control of their health.


Living in Tumultuous Times

Living in the Medieval times was no simple feat for any class or culture of people. In addition to pillagers and thieves, political corruption, and ongoing famine, the people also had to suffer through infectious diseases that were untreatable and inevitably incurable. Had the doctors of the Medieval Era been as educated as the doctors of today, maybe some of these pathogens could have been eradicated; however, these "intelligent men" were not even aware of the fact that these tiny cells or beings even existed.

Many diseases were unfortunately prevalent in Medieval Europe and originated amongst the peasants or lower class, during the Middle Ages, and eventually spread to the higher class and all throughout Europe. No one was safe from the clutches of the bubonic plague (a.k.a. black death) and the pox. In the present times, what most people do not realize is that many opportunistic and infectious pathogens that overcame the populations in the Middle Ages are actually still thriving in the human population today. While some may be less abundant, others are quietly sweeping across the planet, as an incurable and apparently unstoppable, microbiological force.

Thank god, or a higher power (or science), for the discovery and evolution of the field of microbiology...if it were not for this new field of scientific study and research, we would have NO idea how the bubonic plague overcame and killed so many in the Medieval Ages...and we may not even know how to provide an anecdote in case this deadly family of bacteria arises in the future. The one and only way to defeat such a minuscule and menacing being is to FULLY understand its make-up, consumptive process, and reproductive cycle.

Slide of Mycobacterium Leprae

Slide of Mycobacterium Leprae


Leprosy, today commonly referred to as Hansen's Disease, has been infecting humans for millennia. There are documented accounts of leprosy dating back to biblical times. This disease has been overwhelmingly feared since then and more especially during the Middle Ages.

European people who were infected with leprosy were quarantined off into their own villages and residences in which the outside world did not venture. Leprosy was so feared by Europeans that in many cases the leper was made to wear bells so that the rest of the public would know to leave the area that the leper was approaching. Thanks to modern medicine and microbiology, leprosy is not as contagious today due to the administration of sulfone drugs.

If we take a much closer look at the causative agent of leprosy, we would see that leprosy exists due to mycobacterium leprae. Mycobacterium leprae was first discovered in the late eighteen hundreds, by a man named Gerhard Hansen (hence the modern name Hansen's Disease). Hansen was one of the very first scientists to make a connection between a microbe and a particular disease.

Unfortunately in Medieval Times, the art and knowledge of medicine was very limited and skewed due to religious beliefs and superstitions. Fortunately for Europe, leprosy eventually almost disappeared, which is speculated to be due to the quarantining measures Europeans held in place. As demeaning as it must have been for Medieval Europeans to wear bells while enduring this shameful disease, in the end it was a success as it kept others from contracting the highly contagious Mycobacterium leprae.

It should also be noted that Mycobacterium leprae has never been grown on artificial media in a lab setting and that Mycobacterium leprae usually spreads from the nose's membranes to the peripheral nerve system. This form of bacterium is difficult to destroy as it is resistant to macrophage digestion due to its protective waxy coat.

Agar of yersinia pestis, causative agent of the "black death"

Agar of yersinia pestis, causative agent of the "black death"

The Plague

Ashes, ashes...we all fall down.

The Plague, as we call it today, was known throughout Medieval Europe as the "Black Death." The Plague wiped out an estimated four million people throughout Europe. Europeans were more than terrified to contract this disease, as the symptoms were frightening and the outcome was almost always fatality. The symptoms swollen lymph nodes called buboes, bleeding under the skin causing black and blue blotches, high fevers causing an inevitable "daze", and an inability to sleep well.

Though Medieval doctors were not aware of the causes of the plague, we know now that it was caused by the pathogen Yersinia pestis. There are actually three types of the disease - bubonic, septicemic, and pneumonic. The bubonic plague was the most widespread form during the Middle Ages, but septicemic and pneumonic were also prevalent. Bubonic plague immediately affected the lymph system and lymph nodes, septicemic plague is the blood-infected form, and pneumonic plague infected the lungs and respiratory system.

Despite the Medieval Europeans' fears of transmission of the disease, the bubonic plague was rarely passed from person-to-person. This form of the disease was actually first contracted by a flea who jumped off of a rat and then bit a human. The pathogen Yersinia pestis is found in animals even today, mainly in the West and Southwest hemispheres. The good news is if anyone does contract the plague from an animal flea, the disease can be treated and cured with antibiotics...if caught soon enough.

From, an unknown and disturbing quote written during the Plague's devastation:

"Realizing what a deadly disaster had come to them the people quickly drove the Italians from their city. However, the disease remained, and soon death was every where. Fathers abandoned their sick sons. Lawyers refused to come and make out wills for the dying. Friars and nuns were left to care for the sick, and monasteries and convents were soon deserted, as they were stricken, too. Bodies were left in empty houses, and there was no one to give them a Christian burial."

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Variola virus

Variola virus

The Pox

Smallpox was another infectious disease that was a nuisance in the Middle Ages. This disease is caused by the Variola virus, which is a larger sized virus in the shape of a dumbbell. Inoculation is believed to have been used in Europe during the Middle Ages, which is one of the earliest forms of vaccination (as we know it today). Inoculation was performed by taking scrapings of an infected person's skin and inhaling them through the nose. Another way was to implant the scabs into one's skin by scraping with a needle. This medical technique is even believed to date back to 1000 B.C. in the country of India.

Smallpox was usually contracted through the respiratory pathways...the nose and the mouth. It was also a very ugly disease, causing revolting lesions - puss-filled pox marks all over the infected individual's body. Most people who were infected with this pathogen eventually died but many of those who survived the pathogen's wake were left with no sight...blinded from the world. During the Middle Ages, an estimated four hundred thousand lives were lost every year to smallpox; the virus did not discriminate against gender or class.

After the Middle Ages had ended, in the late seventeen-hundreds a man named Dr. Jenner discovered that cowpox could be used as a means to vaccinate a person from contracting the deadlier disease smallpox. He came to this conclusion after his conversations with milkmaids, who claimed that their exposure to cowpox prevented them from contracting smallpox. He then conducted experiments, using the cowpox disease and then exposing his subjects to the smallpox virus...which was successful! The term "vaccine" literally comes from Dr. Jenner's experiments with cowpox...the Latin term "vacca" translates to "cow".

Gonorrhea & STDs

Yes, there were STDs even in the Middle Ages and gonorrhea was the most wide-spread. A man named Avicenna, a resident of Baghdad, wrote about the disease's effects on men's health. So did many others. It was a common known fact that a large amount of sailors carried the disease and sought treatment immediately upon the first signs and the symptoms were quite irritating and painful. According to Kelly McCan's article AIDS Watch: Gonorrhea Gone Wild, the English Parliament "enacted a law to reduce the spread of the infirmity of burning in 1161."

An interesting fact is that Middle Ages' medicine for STDs (and in many cases of leprosy), a topical ointment containing mercury was applied to skin lesions. There was evidence of this medicine discovered in a set of Medieval bones, in the nineteenth century. Though no one is quite sure how gonorrhea originated, there are speculations that syphilis was brought back to Europe by Christopher Columbus or his crew. Apparently they had more fun in the New World than school teachers will tell you about!

Gonorrhea is caused by the bacteria Neisseria gonorrhoeae, which is still infecting people all over the world today. America sees more and more cases every year, though doctors and scientists are sure that many cases go unnoticed, as sometimes the symptoms never appear. Though we have come very far from the treatment of gonorrhea in Medieval times (mercury ointments and "clapping" the penis between two books...I know...Ow!), we still have not totally repleted the bacterium's grasp on society. It used to be that penicillin would cure the disease but now the disease has evolved to grow immune to the antibiotic and only responds to the cephalosporin family. Hopefully more money and effort will be placed into the creation of a vaccination for this disease and other STDs so that no one will have to contract it and we can prevent it from happening altogether. Though the Middle Ages did not have condoms and protective barriers, we do use them!



Dysentery is a disease caused by bacteria that infects the intestines. This particular disease spread rampantly during the Middle Ages, specifically during times of war due to lack of hygiene and unsanitary living conditions. The disease is actually still prevalent in poor countries and places around the world.

Soldiers during the Middle Ages contracted this disease easily, as they were exposed to human feces and fluids on a daily basis. As disgusting as it is, the ditches that the soldiers lived and fought out of were most likely the same ditches that they had to use as a toilet, as well. Obviously these soldiers did not have a proper place in which to wash their hands after using the toilet/hole and so the bacteria was spread from one to another.

Dysentery is in many cases caused by a bacillary bacteria known as Shigella. When we say bacillary, what we are referring to is the shape of the bacteria. Bacillary is a fancy way of saying "rod-shaped" me bacillary looks like the shape of a pill. Take notice of the shape of Shigella in the slide to the right. Shigella was a nasty bacteria to contract, in that it caused such painful symptoms as swelling of the intestines, fever, stomach pain, diarrhea, vomiting and in many cases death.

Shigella still infects the intestines of people today, but most outbreaks in America are usually attributed to improper food handling. Once there is an outbreak of food poisoning, the case is usually investigated thoroughly until a cause for the food poisoning is always comes back to someone not washing their hands before handling food in a restaurant. Yuck. Wash your hands, people!

Streptococcus pyogenes

Streptococcus pyogenes

Childbed (Puerperal) Fever

Have you ever watched a period movie with a horridly sad and terrifying scene of a woman in labor who is also suffering from some unknown illness? Or maybe you've seen a movie that shows a woman lying in her bed, right after going through labor and delivery, only to pass away shortly after? This can be attributed to the fact that Childbed Fever, also known as Puerperal Fever, existed in Medieval Times and claimed many new mothers' lives. At one point, it was one out of three mothers who would contract this disease during childbirth and eventually pass from the infection.

What deadly pathogen caused this horrible illness? There are actually two pathogens that have been known to cause the puerperal infection - Staphylococcus aereus and Streptococcus pyogenes. Believe it or not, both of these microorganisms survive and thrive on our bodies everyday, more specifically located in the nasal passages; however, these microbes are also considered to be "opportunistic pathogens". An opportunistic pathogen is basically a microbe that would not otherwise harm a person of good health, but it has the ability to cause infection in people with weakened immune systems...such as people in hospitals. These pathogens still cause infections in hospital patients today.

Back to the Middle Ages, the new mothers would contract the Puerperal Fever infection from one of these opportunistic pathogens, mainly due (once again) to the lack of medicinal sanitation and hygiene during the child-birthing process. The pathogens would cause infection in the genital tract or the urinary tract, causing the woman's fever to elevate and eventually would make its way into the woman's blood. Once the pathogen took path into the new mother's blood, sepsis would occur (poisoning/infection of the blood), and she would inevitably die from the infection. Many new children would be left without their mothers, for the simple fact that Medieval medicine left much to be protected.

It is still possible to contract Childbed Fever today, but less likely if the child is born within sanitary conditions and techniques. Unfortunately though, the Staph. and Strep. strains of bacteria cause such widespread panic when their infections spread through hospitals mainly because of the fact that they are evolving and becoming antibiotic resistant. People in hospitals have lost their lives because the doctors and medical professionals were unable to find an antibiotic that the pathogen would react to. Study continues and new antibiotics are being developed to destroy these "super bugs".



Medieval Medicine - How Humorous

The world of medicine in the Middle Ages was not a very successful industry, as Medieval medicine was highly influenced by religion and superstition during an age of constant war and increasing famine. Medicine was based on what were called the four "Humors". Doctors and scientists thought that the human body was composed mainly of four fluids or "humors" and tried to treat the ill and dying by lessening certain humors, such as the blood (the process known as bloodletting). In addition to blood, the other three humors were black bile, yellow bile, and phlegm. The idea of four humors, or humoralism, was actually developed by Hippocrates and adopted throughout Europe, thereafter.

Basically the belief held that if a person was healthy, the four humors that his body was composed of would be balanced; however, if a person was not eating properly or in poor health, the four humors would be off-balance. There might be an overabundance of blood or maybe too little of black bile. These four humors were also originally associated to the four elements by the ancient Greeks, though this association died off when Christianity became Europe's dominant religion in the Middle Ages.

Revoltingly, leeches were a common medical tool used to aid in the balancing of the humors, more especially blood. It is absolutely intriguing and absurd that the Catholic church allowed for the use of leeches in medical practice, but they limited the use of herbal remedies for fear of Pagan heresy. Superstition in this case really held back the furthering of medical techniques and logic. Surprisingly, the belief and practice of humoralism continued until the nineteenth century! One thing is certain, medical knowledge and the world of science has come a LONG way since the Middle Ages. We should be thankful that we are aware of what pathogens cause these diseases, so in the future we may find ways in which to fully eradicate these infections from occurring in the world.

Written and copyright © by Kitty the Dreamer (May Canfield), 2012. All Rights Reserved.


odsap13 on August 12, 2018:

muy interesante artículo

Kitty Fields (author) from Summerland on August 12, 2015:

erorantes - Thank you so much! I agree, very sad.

Ana Maria Orantes from Miami Florida on August 11, 2015:

Hello miss kittythedreamer. It is an amazing informative hub. Thanks God medicine this days are excellent. It is so sad how the Queen had the rats as pets, and It is too bad how many people die. I like your hub. It is important information. Thank you for sharing your knowledge.

Tim Sandle from London, United Kingdom on January 05, 2014:

Very interesting.

I've recently written an article titled 'Could the ‘Black Death’ Become a Re-Emerging Infectious Disease?', which readers might find of interest. It can be found here:

the school kid on April 07, 2013:

what is a medieval cure for the fever

Kitty Fields (author) from Summerland on May 10, 2011:

Hi, Peggy W! Oh, I'm so glad you enjoyed this hub.

The leech thing...totally freaks me out! Haha...glad we don't use them in the US (at least not that I know of!)

Thanks for stopping by, you rock.

Peggy Woods from Houston, Texas on May 09, 2011:

Believe it or not leeches are still used today in some places to effectively clean wounds. Microbiology has come a long way towards treating infectious diseases but as you know the pathogens are ever evolving.

Cleanliness and prevention still trumps treating disease if at all possible.

Useful and up rating on this hub!

Kitty Fields (author) from Summerland on March 24, 2011:

alastar - i know...mercury of all things!?! i thought some of the treatments that they used were disturbing, yet very about bloodletting by way of leeches? wow! anyway, thanks for stopping by and i'm very glad you enjoyed (sort of) the pics! :)

alastar packer on March 24, 2011:

What a price to pay for doing what comes natural...mercury treatments...yikes! you brought some new info to the table here in this very well written hub kittythedreamer. liked the pics(well, liked is maybe the wrong! Up and useful.

Kitty Fields (author) from Summerland on March 23, 2011:

oh, very true. it's amazing how far we've come, isn't it? unfortunately there are still many parts in the world that are still without the proper means of sanitation, waste management, and vaccinations...which means that these pathogens have a better chance of causing epidemics. we should feel lucky/blessed for having come so far and having a chance to prevent from contracting these diseases. thanks for stopping by! :)

Don A. Hoglund from Wisconsin Rapids on March 23, 2011:

Sanitaty conditions were pretty bad back in those days.Even as late as the 19th century I believe there was not too much done to keeep garbage and other contaminants under control.

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