• Microbigals

Microbial Monsters: The Light & Dark Of The Black & White Plagues

Updated: Jun 5

The Black Death: Yersinia pestis


Halloween has a lot to do with death, from murder mysteries, to the Grim Reaper, to remembering loved ones that have gone from this world. The darkness that shrouds our Halloween traditions, not only reminding us of the darkness to come and the darkness of the past, but also helps us remember the good that can come from the bad. So I don’t think it’s much of a stretch to connect Yersinia pestis, the causal agent of the infamous black death with death itself as a Halloween theme.


Throughout history, many have tried to conquer great spans of land, but few have had more success in conquest than Yersinia pestis. The year is 1347, a group of townspeople went to greet their family members who had just been abroad fighting in the war. Although they expected some fallen sailors, many were hopeful their loved ones would emerge victorious. 12 ships docked at the Sicilian port but what emerged was horrifying; bodies stacked in large piles, the smell of the decaying quickly swept through the city, weak and sickly sailors staggered out of the ships covered in grotesque black boils, oozing blood and pus. The dead and dying were ordered to sail out to sea and never return again, but it was already too late.



The black death is often described as the greatest catastrophe there ever was, wiping out 20-50 million people in the 14th century, forever altering our future as a species. Waves of pandemics can be seen throughout history, but it was the second black death pandemic that caused the greatest shock waves.


Yersinia pestis The Causal Agent Of The Black Plague


The plague is caused by a bacterium Yersinia pestis, which finds it typical home on rodents, particularly rats and their fleas, but squirrels, prairie dogs, chipmunks, voles and rabbits can all also be affected by Yersinia pestis. Y. pestis favors the fore-gut of the flea where it creates a sticky biofilm.



Human Microbes, History and Science, Microbe News



The biofilm does two things here, the first is the typical biofilm purpose by protecting the bacteria. The second one is a little sneaky. The extensive biofilm is actually so thick that the flea’s food doesn’t reach its gut, meaning no matter how much the flea eats, it thinks it's starving. This causes it to go into a feed frenzy, violently biting and eating whatever it can, all the while regurgitating its previous meal back into its new host and transmitting the bacteria. Microbes can be diabolically clever in the most terrifying ways.


It’s thought rat fleas made the jump to humans, biting them resulting in human infection and . Human to human transmission can also easily occur when someone comes in contact with infectious droplets, tissues, or fluids, and then you have a pandemic.


The genus of Yersinia only includes a few pathogens, Y. pestis, Y. pseudotuberculosis and Y. enterocolitica. The latter two are food- and water-borne diseases that are not nearly as virulent as Y. pestis.


Genetically, Y. pestis and Y. pseudotuberculosis are very similar, so similar they could be considered subspecies rather than different species. However, these two are very different in their transmission and virulence.


Upon the bacteria’s entrance into the body, the lymph nodes will begin to swell, particularly those near the groin, thigh or armpit. This swelling forms bubos, some as big as apples, others only the size of an egg. At this point, the victim has about 7-10 days left in their life which were miserable, filled with fevers, chills, diarrhea, aches and pains and unpleasant odors and liquids oozing from everywhere. Much like our first pandemic, at first the pathogen is seen in only a few cases, but as it goes unchecked and as people travel from town to town (or in our case from country to country) the pathogen can start spreading exponentially. Without any treatment, education or preventative measures, it's easy to see how the plague wiped out 60% of Europe’s population.


Why Lessons From The Black Plague Show We Can Overcome COVID-19


It was not until hundreds of years later, during the third great plague pandemic, that the causal agent was identified by a French microbiologist Alexandre Yersin for whom the bacteria Yersinia and my dog are named after...they are both quite the little pestis. I should also note that same year (1894) that Yersin isolated the bacteria, a Japanese bacteriologist, Shibasaburo Kitasato, also independently discovered it on an unrelated research project. Both Yersin and Kitasato were nominated for the Nobel Prize, but Yersin was the one to be awarded the distinction.


We are at a disadvantage in our current battle of the pandemic due to the global traveling and our city living which creates crowded situations. During the 14th century, the infected fleas could only travel as far as the boat would bring them or simply by foot traffic, a truly insignificant amount compared to the distance and speeds we can travel today in planes, cars, and motorized boats. In addition, a plague traveling by flea needs the right conditions.


Fleas are most active during the warm summer months, meaning there was safety in winter. However, our current pandemic is passed from person to person through droplets meaning regardless of temperature it will survive. In fact, as we enter the colder months we are at greater risk as we stay inside more usually in closer proximity to other potentially contagious people.


But we are also at a huge advantage compared to the Europeans of the 14th century, we have science and germ theory. We have a much better understanding of how pathogens travel and how we can protect ourselves from getting sick. Thanks to scientists, we have a name and a causal agent for our current pandemic COVID-19. In the 14th century, all they had for an explanation of sickness was the Wrath of God! This caused people to do truly terrible and heinous things, like persecuting non-christian communities, or whipping themselves with heavy leather straps!

Terrible Treatments And The End Of The Plague


During this plague, ‘doctors’ would “treat” patients with the ghastly techniques of bloodletting and boil-lancing, which only helped the victims by putting them out of their misery just a little bit faster. Other useless, but less harmful practices include burning aromatics herbs and bathing in rosewater. Although they may seem primitive, hand washing and masks are our number 1 defense against all sicknesses. Many lives would have been saved in 14th century Europe if they only knew what we know today!

So how did the plague end? Very similarly to how we are currently trying to contain and end our own pandemic, by means of social distancing. People suspected of being sick or at high risk, such as sailors were quarantined until they were deemed safe to enter the city.


Today, this plague of the past is not so scary anymore as each year the WHO estimates there are only about 3000 cases worldwide. Although we still see instances of the plague in Africa, Asia and the western United States, it doesn’t cause quite as much trouble as it did and can be treated with antibiotics.


The Ghostly White Plague : Consumption Or Tuberculosis.


Next, we come back to ghosts, particularly the paleness of them. This is the most common depiction of Halloween ghosts, the classic bed sheet with holes cut out. The pale white color of ghosts is one of the more distinguishing qualities. But what could manifest in such a way? Well, we shall show you with tuberculosis or the white plague.


You’ve probably heard of tuberculosis before but what exactly is it? It is an infection caused by the bacteria Mycobacterium tuberculosis that mostly affects the lungs. Here, the bacteria establish residence and can remain dormant for years; this is known as latent TB. The body tries to fight it off, encapsulating the bacteria with immune cells, but it is unsuccessful.


Eventually, the infection can become active, generally when the immune system becomes compromised, causing symptoms such as coughing, chest pain, weight loss, fatigue, etc. The bacteria can even move to different parts of the body such as the brain or kidneys, known as disseminated TB. Without treatment, the active disease is almost always fatal. Luckily, there are antibiotics that treat it. Because Mycobacterium tuberculosis is becoming more antibiotic resistant, the treatment plan can be ghastly. Those that have a non-resistant infection generally have to take them for 6-9 months of antibiotics, while those that have resistant TB can take up to 30 months! I can’t even imagine how shot your microbiome would be after 30 months of dropping little bombs into your gut.


The Romantic History Of Tuberculosis


But this bacteria is nothing new to humanity, it has been around thousands of years and was first mentioned on paper in India 3000 years ago. It has been found in human skeletons over 9000 years old; some even speculate it has been around for over 3 million years. Between the 1600s and the 1800s a quarter of all deaths were caused by TB, or consumption as it was called at the time.





The industrial revolution did not help with this airborne disease either: cities were overcrowded and, if you remember from our cholera blog, general sanitation was extremely poor. However, this disease does not discriminate from the rich or the poor, it infects whomever is closest regardless of social class. Paradoxically, tuberculosis became a symbol of sexual attractiveness.


For some reason, people loved the complexion that consumption gave people, particularly the pale skin, red cheeks and the being thin, no wonder it was called the white plague. This was so sought after that women powdered their face to look pale and, later on, corsets to look thin as well as being romanticized in art, poetry and the stage.


The Dark History Of The White Plague


Seeing ghostly people around town was not always seen as something romantic, in fact, for some it spread illogical fears. During the 1800s in New England, it was thought that the disease was caused by a vampire. More specifically, they thought that a relative that died of consumption had come back to life and was feeding off the remaining family members.


Exhumation of the graves of these so-called vampires found that their heads had been chopped off and the hearts were often removed to be burned. There was even a case where it was believed that the deceased daughter was the vampire, so the father dug up the body, burnt the liver and heart, and fed it to his son who had consumption. Even though the father thought this would cure his son of the vampiric affliction, he died 2 months later.


Science Stops The Dark Romance Of Consumption


During this time, it was thought that it was a hereditary disease, but in 1882 Robert Koch was able to isolate and prove that this disease was caused by bacteria. He even developed a treatment using an extract from TB called tuberculin, which was proven ineffective. It was not a total loss, however, as Dr. Florence Seibert was able to purify the tuberculin and make it into a skin test to determine if you have been exposed to TB which is still in use today.


Once it was discovered, the romanticism faded away and was replaced by the idea that it was a public threat. Eventually, antibiotics were discovered to treat it, but it turned out that a cocktail of different antibiotics were needed as M. tuberculosis developed resistance quickly to any single one.


Unfortunately, there are cases and areas where TB is highly resistant or completely resistant to antibiotics. This is due to several factors including improper dosing or people stopping medication because they felt better before finishing the course or it made them feel worse. As this emerging threat spreads, the need for new antibiotics arise, a theme that seems to becoming more common these days. Some countries, like the United states, have programs where medical personnel watch the person take the medication, ensuring the proper, required treatment.


For More Monstrous Microbes Check Out These Blogs!

Part I: Ghosts and Vampires

Part II: Werewolves and Warts

Part III: Chloroplast As Frankenstein and Micavibrio as Dracula!

Part IV: Microbial Mummies and The Moldy Rye Bread Of Witches

Part V: The Light And Dark Of The Black and White Plagues

Part VI: The Disturbing Dental Creatures That Create The True Halloween Horrors: Cavities





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