Plagues, and How to Die in Them: A Short Explainer.

Dirty Science by Dr Brenna Hassett

People[1] are suddenly remarkably interested in infectious diseases.

This isn’t unreasonable – infectious diseases kill people[2]  at terrifying rates, and have, at various points in the past, ramped up to such catastrophic levels that they have fundamentally altered the societies they plagued. We are all aware of the existence of historical plagues, of course, because they are apparently a great excuse for framing a short-story collection,[3] but as the world suddenly turns to face (or, in some places, nervously side-eye) the new infectious agent Covid-19, perhaps it’s worth looking into the carnage they leave behind to understand what plagues do to people – the ones who die, and the ones that live through.

Pandemics

Humans have a long history with infections; we wouldn’t actually exist without the adaptations that interactions between ourselves and viruses have brought about. But what we want to know about now is pandemics. What kills you in the kind of plague that sweeps through a place and carries off the untold hordes? Well, one clue to as when these become popular is in there in the word ‘hordes’. It is very difficult to have a pandemic, a real killer, without lots and lots of people. If a virus were to, say, suddenly leap from a random pangolin to a random hunter gatherer and then proceed to kill said hunter gatherer in a matter of days, then there’s only a limited number of people that virus is going to be able to jump to before running out of viable hosts– hunter gatherers don’t live in very dense groups, most of the time.[4]

A pangolin in defensive posture. Pic by Stephen C Dickinson.

But, when the fatalities mount, archaeologists can finally become useful. We excel at the science of counting the dead – how many, and who. Humans have a fairly predictable life pattern, and the risks to us (without modern medicine) fall in predictable places. Babies are vulnerable very early on; children under the age of four fall victim to gastroenteric diseases, infections, and other things that take advantage of any gap in their nutrition levels as their diets shift from largely mom-focused to more adult foods. In societies with a lot of fatal violence carried out by young men, upon other young men, it is unsurprising that young men run the risk of ending up in the ground to be counted. Young women have the gauntlet of childbirth to run. Given time, everyone falls foul of something, but, in the normal course of events, the vast majority of people between four and sixty survive. It makes a nice little U shaped curve if you count the bodies and then draw it out.

As drawn (badly) by author.

Then, you get a pandemic. A pandemic is just another infectious disease, but one that spreads rapidly. The one we normally talk about in history and archaeology is the bubonic plague, caused by Yersina pestis,[5] because it makes periodic jumps out of its adorable marmot reservoir on the steppes and sweeps across huge geographic areas, killing an extraordinary number of people in fairly painful and awful ways.[6] One of the reasons we love talking about plague is that our palaeogeneticist colleagues have gotten quite good at identifying Y pestis bacteria from skeletons; we can trace outbreaks of plague to Bronze Age Russia 4000 years ago, in the Plague of Justinian in 541 AD, the Black Death in 1348, and the one that memoirist Samuel Pepys was so worried about in London in 1665.

Bills of Mortality August 15-22, 1665. This file comes from Wellcome Images, a website operated by Wellcome Trust, a global charitable foundation based in the United Kingdom. © Wellcome
This file comes from Wellcome Images, a website operated by Wellcome Trust, a global charitable foundation based in the United Kingdom. © Wellcome

The Cosmic Shambles Network relies on your support on pledges via Patreon so we can continue to provide great, new, exciting content without the need for third party ads or paywalls.
For as little as $1 a month you can support what we do and get some great rewards for doing so as well. Click the Patreon logo to pledge or find out more.

When a disease goes big, it’s a pandemic, and a pandemic is a big problem, for a large number of people, especially when the infection is so virulent that people who shouldn’t die, die. That graph looks like what happened when Spanish Flu hit the world in 1918:

The difference between the influenza mortality age-distributions of the 1918 epidemic and normal epidemics – deaths per 100,000 persons in each age group, United States, for the interpandemic years 1911–1917 (dashed line) and the pandemic year 1918 (solid line)

So who dies?

In the normal course of an infectious disease, there are certain groups that we would expect to bit hit hardest. Those with other health issues, the aged, the malnourished, and those without mature immune systems. This is the same section of the population that is encouraged every year to get a flu shot, for very good reasons. What seems to really terrify us, what gets memoirs written and poor excuses for erotic storytelling canonised as great literature,[7] is the threat that death will not content itself with the most vulnerable.

So what makes a killer out of a disease? Spanish Flu terrified millions because it killed the young and otherwise healthy, and it spread with the unprecedented speed across the globe on the backs of millions of young men who had fought in World War I. These unlikely victims may have been predisposed to their fate, however, by early exposure to a different, smaller epidemic of flu in early childhood.

The black death arrived in Europe just as medieval cities were reaching out into new and exciting markets; the trade networks of Genoa in the 1340s, for instance, included the fortified post of Caffa in what is now Ukraine, where besieging Tartars began to succumb to some mysterious disease and, in a fit of pique, threw their dead over the walls. The Genoese sped home, carrying both the bounty of their global trade network and yersina pestis. So we could blame globalisation again, but from skeletons in London’s plague pits we know that many of the plague dead had also suffered in the famine years of the 1320s, and may have been in poor shape to begin with.

So it takes a combination of things to kill you in a pandemic – vulnerability, and opportunity. There is not much we can do about vulnerability, without doing something totally unrealistic and crazy like trying to ensure the vast majority of people on the planet have access to adequate food and medicine. Opportunity, then, is where we focus our efforts in the current climate. Denying infectious diseases the opportunity to kill us is our best chance at keeping ourselves alive, especially if we sit at either end of that mortality risk U-curve. Exactly how we accomplish that, however, is something you’re going to need a doctor with living patients to tell you.[8]

[1] Affluent, western

[2] Poor, elsewhere

[3] I’d include both the Decameron and the Bible in this category.

[4] If that pangolin were to fling itself into the middle of the massive seasonal gathering of multiple groups of hunter gatherers however… well.

[5] With honourable mention going to rains of frogs, locusts, blood, etc.

[6] Lesson: don’t eat Siberian marmots, jerboas, or gerbils.

[7] Looking at you, Bocaccio.

[8] Wash your damn hands.

Dr Brenna Hassett is an archaeologist specialising in the analysis of human remains as a researcher at University College London and a Scientific Associate at the Natural History Museum London. She has dug on sites across the globe, from Greece to Egypt to Thailand and beyond. She is one quarter of The Trowelblazers group. Her first book, Built on Bones, was published in 2017 and she is currently writing her second, due for release in 2021. She is on Twitter at @brennawalks

If you would like to reuse this content please contact us for details

Subscribe to The Cosmic Shambles Network Mailing list here.

The Cosmic Shambles Network relies on your support on pledges via Patreon so we can continue to provide great, new, exciting content without the need for third party ads or paywalls.
For as little as $1 a month you can support what we do and get some great rewards for doing so as well. Click the Patreon logo to pledge or find out more.