Plagues are one of the more terrifying disasters human society can face. Something like a hurricane or a volcanic eruption is more destructive on a physical level, but an epidemic or pandemic is all the more frightening for being stealthy. Once a person gets sick there are usually visible signs (though not always — see HIV), but prior to that there’s a period of time where they may be carrying and spreading contagion without knowing it.
This happens for a biological reason: a disease that kills people very quickly is one that has relatively little time to spread. From the standpoint of the bacterium or virus, it’s better if it can hitch a ride for a while, quietly reproducing, before the immune system notices and tries to take it out. During that time, the disease is invisible to the naked eye . . . and as we’ve seen with witchcraft, people have a tendency to freak out when they can’t see where the danger is coming from.
Sea travel, and in recent decades air travel, are notorious for spreading diseases — either through infected passengers and crew, or through (in the case of ships) bringing rats and fleas to new shores. Overland travel is historically slow enough that there’s more time to notice someone getting sick before they have much opportunity to share their germs with new people, but even then, travelers are a source of danger.
Which is why, in times of pestilence, cities and countries often closed themselves off to travelers, or else imposed a period of quarantine — derived from the Venetian phrase for “forty days,” the length of time ships were isolated during the Black Death. In England houses where plague was found were boarded up with all the residents inside and guards set to watch the door, which of course nearly guaranteed that everyone inside would sicken and die. A better (and later) practice was to remove the sick to a “pest-house,” where they would be isolated away from the healthy. But that required an investment of infrastructure, and in the middle of a catastrophe, resources were often too thin on the ground.
The Black Death is the most famous plague most of us could name, but just as you can map out history as a sequence of wars, so too can you view it as a sequence of pandemics: the Plague of Justinian, the Antonine Plague, the two Cocoliztli Epidemics, the first, second, and third cholera pandemics. We think of the flu as a nuisance now, but the Spanish flu outbreak of 1918-1920 is estimated to have killed somewhere between fifty and a hundred million people — and it isn’t impossible for something like that to happen again, though our ability to treat the symptoms is greatly improved now.
When illness happens on that scale, society breaks down. Trade grinds to a halt, because visitors are locked out or held up for weeks on end, and local authorities may also try to prohibit people from leaving lest they carry the sickness elsewhere. Accounts of the Great Plague of London in 1665 make it clear how difficult it was for the city’s remaining government to keep the food supply going, so that citizens wouldn’t starve. Last week I mentioned Pestilence appearing alongside War and Famine in the Four Horsemen of the Apocalypse; it’s not uncommon for famine to come hard on the heels of illness (as there’s no one to work the fields) or vice versa (as food shortages make people more susceptible to disease).
And then there’s the “war” aspect. When a plague spreads like wildfire through a community, people will look for someone to blame, because that’s better than feeling completely helpless. Foreigners are often the first target, due to the aforementioned risks of travel. In Europe, Jews took the brunt of this fear again and again, being expelled if not murdered as scapegoats for their Christian neighbors. When there aren’t any “outsiders” available, the poor, female, and/or elderly may be accused of witchcraft. Or piety can rear its head in ugly form: maybe this is a punishment from on high, and the gods want you to root out the sin among you, by any means necessary.
Death rates vary wildly, but even in the worst cases, they usually aren’t anywhere near total. The New World, however, was a special case. For quite a while during the twentieth century, Western historians kept reducing estimates of the original indigenous population of North and South America, because contemporary accounts simply weren’t plausible to them — how could there have been that many people, with upwards of ninety percent of them supposedly dying when disease reached their settlements? Even in “virgin soil” epidemics, where no one has childhood exposure, the death rate rarely goes above thirty or fifty percent. But more recent research has shown that, because of the migration bottleneck into the New World, the genetic immunity profiles of indigenous peoples are vastly more homogenous than you see elsewhere. Which means that when contagion struck, the death toll could be near-total.
Obviously there were other factors conspiring to shatter traditional indigenous societies, but this annihilating loss of life was certainly one of them. Plagues are, on a large enough scale, a force for massive social change: they can end dynasties, bring down empires, spawn new heresies (or formal religions, depending on how well they fare), and even transform the shape of society itself. The Black Death is theorized to have contributed to the rise of a “middle class” in Europe, as the economy transformed from one where labor was plentiful and land scarce to the exact opposite.
Change on that scale rarely shows up in fiction, because it’s hard to show the sweep of events over a century or more. It can form a scar in the past, though, with festivals in thanks for the end of a great pestilence, or the ruins of cities abandoned after a catastrophic loss of population, or an ethnic group forced into migration. And of course a plague can feature as a present occurrence in a story, with all the difficulty and peril that brings.
If you really dig into the details, it’s a terrifying thing to write about. But maybe a little terror isn’t a bad thing, as it teaches us not to take our current state of health and safety for granted.