What many people do not know is that the number one cause of death throughout recorded history is disease. The has killed more humans in the history of the human race than any other cause. War doesn’t even come close, neither does famine. And even when soldiers die in a war, they frequently die from disease. And disease pandemics have changed history over and over again.

The Plague of Athens (430 B.C.E.)

One of the earliest examples is the fall of Athens in the Peloponnesian War in 430 B.C.E. You probably know that Sparta defeated Athens in what we might think of as a kind of Civil War (it wasn’t really) between cities that as allies had stopped the Persian empire. Sparta laid seige to Athens, and that meant that all of the Athenians took shelter inside the city walls. And nothing promotes epidemics better than jamming a lot of people into a small space. The Plague of Athens killed around 75,000 to 100,000 people in Athens, about 25% of the population, and among the notable casualties was the Athenian leader, Pericles. The Athenians might well have won this conflict if it were not for the plague. But what happened to them made defeat inevitable.

The Antonine Plague (165-180 C.E.)

The Antonine Plague was running rampant in the Roman Empire from 165-180 C.E. It gets its name from the Antonine family, one of whose members, Marcus Aurelius Antoninus, was emperor at the time. It was estimated to have killed as much as one-third of the population in some areas, and devastated the army. Historians have noted that it brought an end to the Pax Romana and ushered in the instability that ultimately brought down the Roman Empire in the West. Estimates are that 5 million citizens of the empire died. And it may even have helped the rise of Christianity in the Empire.

Marcus Aurelius had planned military actions in the Balkans to stabilize and extend Rome’s borders, but he died of the plague and his plans were abandoned.

The Plague of Cyprian (250-271 C.E.)

The Plague of Cyprian (250-271 C.E.) is named for the Bishop of Carthage who wrote about it. It is a major cause of the Crisis of the Third Century. In this time the Roman Empire nearly collapsed, and did in fact split into three parts. The plague devastated both agricultural production and the army, and at its height 5,000 people per day died in Rome.

The Justinian Plague (541-549 C.E.)

The Justinian Plague was the first of repeated waves of plague outbreak that we have identified as the Bubonic Plague based on DNA study of excavated corpses. The immediate impacts are significant enough. Both the Roman Empire in the East (also known as the Byzantine Empire, though to be clear the people who lived in it always called themselves Romans) and the Sassanid Persian empire, Rome’s chief rival, were devastated. Further waves of this plague persisted over 200 years, and were estimated to cause up to 100 million deaths, which would represent about half of Europe’s population at the time. The immediate effect was to stop Justinian’s plan to bring the Western part of the Roman Empire back under imperial control, thus putting Europe into the slide towards the Dark Ages. But it also is probably the primary reason for the success of the Arab conquests in both Roman and Persian territory since the Arabs were fighting greatly weakened states.

The Black Death (1347-1351 C.E.)

The Black Death is probably the worst pandemic in recorded history, killing as many as 200 million people in Eurasia and Africa, or about one-third of the global population. In Europe up to 60% of the population is estimated to have died, and social effects were profound because of the severe labor shortage that resulted. Europe’s population did not recover to the 1300 level until 1500. This undermined the feudal system and helped to usher in the age of Capitalism.

The Americas (1492 – ?)

One of the most consequential examples of disease changing history is when Europeans came to the Americas. A lot of people who don’t know anything about history picture the Americas as lightly settled by uncivilized pastoralists. Nothing could be further from the truth. A book I love is called 1491, by Charles C. Mann. He shows that the Americas were inhabited by highly civilized people. The Aztec capital of Tenochtitlan had running water, immaculately clean streets, and was larger than any European city of the time. Mesoamerican civilizations came up with the concept of zero long before the Arabs did. The estimates for the different civilizations in the Americas add up to around 60 million people in 1492. Europe’s population at that time was estimated to be 70-88 million. So what happened?

Jared Diamond offers a good explanation in the widely read Guns, Germs, and Steel. A key factor is that the Europeans brought with them diseases for which the Native Americans had no resistance, among them being measles, smallpox, influenza, and the bubonic plague. As a result, 56 million Native Americans die, which was over 90% of the population of the Americas, and 10% of the global population of the time. This is the largest death toll in percentage terms ever, and second only to World War II in absolute numbers of dead. This not only made it very easy for Europeans to come in and take over. But it had global effects as well. As the population died off, cultivated lands returned to a wilder state, and this regrowth removed enough CO2 to cool the planet. This has been called the beginning of the Anthropocene Epoch in global climate, and contributed to the Little Ice Age.

In British North America a similar story can be told. Americans learn about Pilgrims landing at Plymouth Rock and setting up a settlement, but you rarely learn that they moved into an abandoned Native settlement that was empty because of diseases brought by European fishermen, and that they were helped to survive by plundering native graves.

Cocoliztli epidemic (1545-1548 C.E.) 

There were a series of epidemics all called Cocoliztli, but this was the biggest. In this wave it is estimated that 15 million natives died. Other epidemics in this series occurred in 1520 and 1576.

Slavery

A side effect of the native susceptibility to Old World diseases was that Spanish plans to enslave the Natives and use them for labor were frustrated by the high death rates. This lead them to bringing African people over instead, who had resistance to the diseases endemic in the Eastern Hemisphere. So disease is a proximate cause for the enslavement of Africans in the Western Hemisphere.

Spanish Flu (1918-1920 C.E.)

The so-called Spanish Flu is a misnomer. The best evidence I have seen suggests that it first appeared in Kansas at an Army base, and spread because of World War I. But because of military censorship there were no reports of this disease among the combatants in Europe even though that is where most cases occurred. In Spain, which was not a participant in the war, news accounts were free to cover the outbreak of the disease there. This flu was an H1N1 virus, thus part of the same family as the Swine Flu epidemic of 2009-2010.

This flu is estimated to have infected 500 million people world-wide, or about one-third of the global population. A novel feature of this flu is that unlike most flus, which kill primarily the very young and very old, this flu killed young adults by creating a cytokine storm (and we might note here that cytokine storms are implicated in many Covid-19 deaths as well). Estimates of the dead have been in the vicinity of 50 million, or about one in ten of those infected. For comparison, World War I dead totaled about 20 million, with a further 21 million wounded.

Summary

The point of this essay is that infectious disease is a major influence on history. It has caused more deaths than anything else. It has brought down empires and helped new ones arise. It has aided the spread of religions, and contributed to a racial problem we still suffer from.

And on the other side, the increase in human lifespan we have seen in the last few generations is largely due to our ability to prevent, manage, and cure disease. We only think of cancer and heart disease as major killers because for the first time in human history large numbers of people live long enough to get these illnesses of old age. Sadly, we are also perilously close to throwing it all away. We now hear people say “It is only the flu” like influenza is no worse than a head cold. Yet in the winter of 2017-2018 80,000 Americans died of the flu, and the averages are:

CDC estimates that influenza has resulted in between 9 million – 45 million illnesses, between 140,000 – 810,000 hospitalizations and between 12,000 – 61,000 deaths annually since 2010.

https://www.cdc.gov/flu/about/burden/index.html

Another disease we now need to watch out for (again) is Measles. We had nearly wiped it out in the U.S. and in fact it was declared “eliminated from the U.S. in 2000”, but in the last few years as vaccination rates have fallen, it is making a comeback in the U.S. The CDC says that Measles is a leading cause of vaccine-preventable infant mortality. I hope the vaccine hysteria in the U.S. will die out, but I suspect it will take a lot deaths get there.