Blog / Disease Epidemics / Natural History

“A Plague on your Houses”


 That was William Shakespeare in his play, “Romeo and Juliet,” written in 1592.  [Act 3, Scene 1].   Appropriate at this time of our pandemic. For Europe had, by Shakespeare’s writing, already suffered two hundred years of the Black Death!  Let’s investigate.

The “Plague” is caused by a lowly bacterium, one of those organisms that we scoff at since we soak ourselves in antibiotics.  We will see how well we are served by that hubris in the future.  Even today, we promote our invincibility, or just believe those we want to believe, that social protections are not needed, not effective, or an affront to our dignity.  But there are little things out there still trying to kill us [or just reproduce within our tissues!].

Covid-19 mortality is significant in America.  500,000 dead.  But in a country of about 330 million people, that seems, to some, to be bearable.  You wouldn’t think so if you were the one dying.  Or if you were living in Europe in the 1300s.  Then as much as 50% of the population died of the “Black Death” that was sweeping the country.  And, unlike Covid-19, it took down everyone, not just the dispensable aged.  Blame that on the fleas, but those Siphonapterans didn’t know what they were doing.  Perhaps God really was dishing out retribution!

Before the scientists Louis Pasteur and Robert Koch, the best the “learned” minds could suggest was that the “Plague” or “Black Death” was caused by foul air.  They called them “Miasma’s.”  So said Hippocrates and Galen, and they were the “learned” men at one time.  But that was 2,000 years ago, and such primitive thinking should not have lasted so long.

Terrible things putrefying out of wet earth and swampy soil, they said.  That’s why all the rats died just before the plague swept through a town.  That made sense.  The rats were closer to the offending source of the Miasma, that illness giving off down there.  The rats got the first “whiff.”  But they got the rat part wrong, too.  As you will see, we can explain that phenomenon correctly now!

“Zoonotic” vectors of disease.  That’s what did it.  Disease vectors attacking humans through other creatures.  And in the case of the Plague, it was carried by rodents, especially the black rat [Rattus rattus, a fearful concoction of terrifying syllables], transferred by fleas [the rat flea, Xenopsylla cheopis] to the only species of human beings now living [Homo sapiens, you and me].  Add the infectious bacterium [Yersinia pestis, aptly named] and you have four organisms whose behavior explains the terrible consequence.

Bacteria.  What are they?  Not viruses.  Viruses may not even be alive [but they do seem to be opportune killers!]. Bacteria are not plants.  Not animals.  So how do they fit into the Kingdoms of Life?  I am glad that you asked.

We used to think there were only two Kingdoms.  Plants and animals.  Obvious, and simple to see.  Antonie van Leeuwenhoek, in 1674, spoiled that repose with the first drawings of what he saw with the first microscopes.  Okay, add a third Kingdom, and call it Protista.  But some of those tiny single-celled creatures had nuclei, organelles within the simple cells containing genetic material.

In life, there are “lumpers” and “splitters.”  So let us break that Protista Kingdom into two.  One with cells like ours [“eukaryotes,” true cells], and those more primitive ones [prokaryotes].  And then there were four Kingdoms!  Plantea, Animalia, Protista, and Monera [the prokaryotes].

All right, but fungi are clearly different [even if they are eukaryotes, too].  So let’s give them a Kingdom of their own!  And in 1977, ribosomal RNA analysis in the bacterial Kingdom, Monera, separated the prokaryotes into the Kingdoms Eubacteria and Archaebacteria.  So now we are up to six Kingdoms, depending on whether you are a lumper or a splitter!

Note that viruses are not even included in this Tree of Life [and how would you deal with the infective proteinaceous prions causing Mad Cow Disease?].  I suppose that whether these things are alive depends on who is doing the asking.

So what about the Plague?  It is a single-celled bacterium, Yersinia pestis, in the Kingdom Eubacteria.  And it is a tricky one, having been around in a big way for a long time, evolving in many different environments with variants immune to some antibiotics.  Nasty.

And get this.  It is a “facilitative anaerobe.”  It can breathe oxygen to reproduce greatly or, under more stressful anaerobic conditions [without oxygen], use the primitive form of fermentation [like yeast do] to trap energy for its metabolism.  This is a devilish adversary.

So here is how it gets to you.  Plague comes in two main types of infection.  Bubonic and Pneumonic Plague [there is also a third, Septicemic Plague].  In Pneumonic Plague, bacteria can pass between people on little droplets breathed out by an infected person [sound familiar?].

In the Bubonic form, such as that of the Black Death of the Middle Ages, the bacteria gather in the human lymph nodes, where they reproduce, forming swellings called “buboes.”  If untreated, fatality is 30-60% for the Bubonic form, and almost 100% for the Pneumonic form.  Antibiotics can be an effective treatment if caught early.

The Plague bacterial populations are maintained in rodent reservoirs.  Rats, especially.  And these rodents are ancient seafarers, riding in grain cargos and climbing up mooring lines.  But humans don’t get the disease directly from rats.  An intermediary is needed.  The flea.  And in this case, a very unlucky one.  For after ingesting the infected blood of a rat, the bacteria virulently reproduces within the flea’s body, eventually clogging up its gut and causing it to regurgitate the disease back into the host through the next bite of the flea.  And if you are that next host, you are toast.  Gross!

There have been three pandemics of Bubonic Plague, each one lasting multiple generations, only to disappear and reappear later.  The first was during the reign of Justinian, Emperor of the Byzantine Empire based in Constantinople.

He ruled for almost 40 years, between 527 to 567 A.D.  He built the Hagia Sophia Church [now mosque] in Constantinople, and is remembered for codification of Roman law known as the Code of Justinian.  Justinian reinforced the imposition of Orthodox Christianity, punishing pagans and adherents of other religions.  The Temple of Isis, on the island in the Nile called Philae, was finally closed and marked the end of the religion of the ancient Egyptians.

The sweep of the Plague’s initial destruction lasted for eight years, beginning in 541 A.D., infecting even the Emperor, himself.  One-quarter to one-half of the European population died.  And the Plague would continue to return in different locations and virulence for the next 200 years.

The “Black Death” of the Middle Ages was the second pandemic of the Bubonic Plague.  It was probably spread along the trade routes of Central Asia, exploding into Europe via Italy in 1347 A.D.  For six initial years, it rampaged through easily accessible, weakened humans.

European populations had recently doubled and many towns had grown in excess of 15,000 inhabitants.  No sanitation, crowded conditions, and then an economic recession made European humans easy targets.  A “Great Famine” in the 1320s, followed by a “Great Bovine Pestilence” [probably rinderpest], greatly weakened the disadvantaged hungry population.  Human immunity was undoubtedly compromised.

Maybe one-half of Europe’s population was killed in that first wave of infection.  The disease would recede and then return in waves for 400 more years.  No wonder that the Swedish filmmaker, Ingmar Bergman, used these times as an metaphor for the feared cold war destruction in his 1957 film, “The Seventh Seal.”  In it, a medieval knight plays chess with death, traveling through the countryside of wailing peasants convinced of God’s wrath.

The third plague pandemic is considered the modern one, but primarily attacked Third World impoverished nations.  It surfaced in the late 1800s, killing at least 12 million people in India alone.  The plague reached the American Southwest in the early 1900s, where it apparently established its reservoir in rodents.  From 1900 to 2016, there were about 1,000 plague cases reported in the United States.  It continues to be a significant concern, today, in Peru, the Congo, and Madagascar.

Did Shakespeare really know of the disease?  The Plague is what sets up the tragedy that he wrote as “Romeo and Juliet.”  And there is more than romance to recognize therein!




About Author

Ronald R. Van Stockum, Jr. is a lawyer, teacher, biologist, writer, guitarist, and recently an actor living on his family's old farm in Shelbyville, Kentucky. He has a Bachelor of Science in Biology from Santa Clara University, and a Masters and PhD. in Biology from the University of Louisville. He also has his Juris Doctorate in Law from the University of Louisville Brandeis School of Law. He practices law from offices in Shelbyville, Kentucky concentrating his legal practice in environmental law. His biologic research is in historical phytogeography. Dr. Van Stockum, Jr. has published numerous books, articles, and short stories in the areas of law, science, and creative writing. most of his 24 titles are available on this site and Amazon with many on Kindle and Audible!

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