In this series, I’m talking about big issues in how we think about our scientific past. This week I’m dealing with the specter of epidemic disease. Read the first post in this series, on ancient Greece and math. Read the second post, on the Scientific Revolution. Read the third post, on astronomy and astrology.
It’s been lurking back there this whole time. It was the precursor to the Protestant Reformation. It was the reason Newton was looking at that apple tree. It was maybe the final nail in Rome’s coffin. The plague.
The plague is so often invoked as the villain of the pre-modern world that it has become the antagonist in the history of science. And it has a whole band of evil friends working with it. Cholera. Leprosy. Scurvy. Smallpox. Syphilis. AIDS. Diseases – especially infectious diseases – are almost too obvious a villain. They’re like a hook-nosed caricature. They kill people! They’re lurking in the shadows and maybe even in our drinking water! You won’t know they’re right behind you until it’s too late!
It’s easy to say that when epidemiologists are studying the spread of disease, what they’re fighting against is the disease itself. But if you think about disease as a social issue, a public health issue, rather than as one person’s fight for their body, the villain (if there is one) is the social conventions that prevent people at large from implementing successful preventative measures.
Fun fact: the plague still exists today. It was endemic in parts of Asia and the Indian subcontinent throughout the 20th century – there was even a major outbreak in Vietnam during the Vietnam War. Seinfeld even made fun of the fact.
It’s even endemic to the US. Every year, unwary hikers in the southwest still contract plague by coming into contact with prairie dogs and other rodents. But we don’t think about this when we think about plague. Because the plague is a premodern disease. It’s a disease for the unwashed, from back when people were afraid of bathing. If anything, knowing that the plague is still around makes some places seem more backward, but it doesn’t make the past seem any less wretched. [Quick point of information: the disease itself is called plague, identified as the microbe Yersinia pestis, and it presents in one of three ways – bubonic, pneumonic, and septicemic. The major outbreak in the mid to late 14th century across Europe, Asia, and parts of Africa is known as the Black Death. Other outbreaks have other names, such as the Justinianic Plague of the 6th century.]
But major infectious diseases are still a stark reality of human life, and continuing to help protect people from them depends on understanding that it’s not an issue of science vs. nature, but of the individual vs. society. I talked about this in an earlier rant on the real purpose of vaccines. Vaccines don’t work because they protect one person from contracting an illness, they work because they create herd immunity – they prevent enough people in a society from contracting the disease that the disease can no longer reproduce and dies. While vaccines are very much a product of modern medicine, the idea of infectious disease as a social issue is distinctly pre-modern. Pre-modern peoples tended to think about disease in terms of society because it was part of their intellectual framework.
One of the biggest differences between pre-modern and modern ways of thinking is that while modern societies are concerned with people as individuals, pre-modern peoples didn’t think so much about individuals as they did about society as a whole. This isn’t to say that pre-modern peoples were just worker bees in the hive with no concern for themselves. It’s more that when people approached an issue, their impulse was to relate to it as a member of society rather than as an individual with a personal history. Think about the modern superhero origin story. The hero gets their motivation from their individual upbringing – Spiderman gets his values and his sense of justice from his uncle, Black Widow gets her need to be on the side of justice from her painful assassin training, Batman hates criminals because his parents were shot in front of him, and every single one of the X-Men has a convoluted personal story about the way their mutant powers alienated them from other people. These are individualistic explanations for why each hero exists – a societal ill affected them personally, and because they were given some great superpower like telekinesis or lots of money, they became vigilantes. In contrast, pre-modern peoples (the ones whose opinions we know because they wrote about them and their writing survives, anyway) tended to talk about societal problems simply as societal. So, when diseases like the plague descended on a city in the Middle Ages, scholars of disease thought of it not as a single entity infecting many individuals, but as a massive cloud of infection that sat over the city itself. This isn’t because they didn’t understand the concept of contagion, but because they conceived of it as a social problem, rather than an individual one. It wasn’t about which specific person made them ill, but about the city as a whole encased in disease.
In fact, pre-modern ideas about illness were generally fairly personalized. You got sick because your personal complexion (the balance of humors in your body) predisposed you to bad reactions to stimuli like the weather or particular foods. But when you caught an epidemic disease, it had nothing to do with your personal complexion anymore – now it was about the society that you belonged to. There is some pre-modern sense of epidemics as an act of God (or gods), but for the most part this was meant in the sense that it seemed random who actually got sick and died. The plague is a particularly good example of this because it is the most harmful to otherwise healthy adults, so even according to a modern understanding of illness, it’s unpredictable. If anything, God’s involvement in diseases like the plague was about humans following orders rather than retribution or moral lesson-teaching. In the medieval Islamic tradition, it was important to stay in a city once it got the plague not because people wanted to avoid spreading it, but because it was God’s will that the plague was in the city while you were also in it. Even though the notion of quarantine was invented as a measure to protect against the Black Death, there was no strong tactic of separating the ill from the healthy before this – anyone who was in an exposed area was considered sick. This idea of disease as God’s will extended to a sort of generalized social contagion – bad luck was a curse that could be caught by proximity, because God had cast it on specific people in a specific place, and entering that place would put you in a sort of fortune crossfire. But premodern notions of epidemic diseases also skewed the other way, towards grace. Leprosy, for instance, was respected as much as it was reviled. Leper colonies were treated like living relics, where the sick could perform intercessory prayer on behalf of the healthy, since they had already gotten God’s attention.
It’s easy to look back at attitudes towards these diseases and see them as a mere reflection of medical ignorance. But these diseases are genuinely baffling. Plague is communicable in three different presentations – there’s no reason to even believe they’re the same disease, and for much of the 20th century, plenty of historians of disease argued that they weren’t. And leprosy is perhaps a very mildly contagious disease, to the point that people catch it only through repeated constant exposure, and even then it develops extremely slowly. These diseases certainly loom large because they are mystifying, as well as because their symptoms are so visible.
But it’s also important to recognize our own shortcomings in terms of modern epidemiology. I once heard someone argue that the Middle Ages lasted until 1865, when the antiseptic Listerine was invented to sterilize surgical sites. I think this idea is ridiculous because it ignores every social, political, institutional, artistic, and technological paradigm shift except one. But it still makes a good point, that a lot changed in a very short period of time when modern medicine developed sterilization, germ theory, and vaccines. Broad-spectrum antibiotics, those capable of treating anything other than a staph infection, have only been available since 1961. The most essential pieces of what we call modern medicine have only been in wide use since the middle of the 20th century.
And although we have these tools, we have a lot of difficulty using them effectively. We overprescribe medications such as antibiotics and pain killers, or use them indiscriminately in farm animals. And even though we understand the mechanisms of the spread of disease, we often have trouble implementing solutions, or doing it quickly enough. Consider how much American cities hesitated to shut down travel during the height of the Ebola crisis a few years ago, or how many times there has been an outbreak of E. coli or salmonella in the last two years. Implementation is just as important as knowing how to fight an outbreak, and there are many diseases for which we have no cure. And when we do have a cure, we often don’t know why. Penicillin was developed 20 years before a different medical scientist discovered how it worked. We still don’t know exactly how most anti-depressants work. And often when a drug is being developed, its unintended side effects are so potent that they become the new purpose of the drug – that’s why we have Viagra.
Looking at the history of diseases shows just how little we still know about medicine. Part of the reason for that is that the human body is complex and our efforts to fix it can be drawn out and even have unintended consequences. But it also matters what is happening socially around the disease. HIV/AIDS is a startling example of the social function of disease. This is a disease that once existed in small pockets of people who had been exposed to it after accidentally nicking themselves when butchering infected apes during hard times when food was scarce. Until recently, it was the most terrifying pandemic on Earth, with no cure and a weak treatment. It’s spread was facilitated by so many major social changes, including the urbanization of sub-Saharan Africa, global business, underground gay culture, drug use culture, and governments (particularly in the US) that feared all of these things. But effective treatment was also a social movement. It’s taken normalizing the use of condoms, legalizing homosexuality, applying harm prevention methods in treating drug addiction, and word-of-mouth campaigns within marginalized communities to begin to stop the spread of the disease, not to mention creating wider access to medical care and developing a drug to prevent the spread. For decades, the barrier to treating AIDS wasn’t that medicine didn’t have a cure, but that there was too much social stigma around the people who contracted the disease. One of the most significant moments in the history of the disease was when a young boy contracted AIDS through a blood transfusion, and despite all the people who had already died, it was his perceived innocence that brought attention to the suffering. Even now, we moralize disease, and declare that some people are less deserving of treatment because of who they are in society – what they do, how they act, who they know. The same change happened when cholera hit London – the British hadn’t cared about the disease in any other part of the world before, and they barely lifted a finger to stop it until it started killing the wealthy (thanks to a John Snow who did know something). Diseases matter to us because of who they hurt.
The modern definition of disease has broadened since the advent of germ theory. We’ve come back around to the medieval notion of social contagion, where what spreads can be an attitude or an action, not just a microbe. Gun violence is a communicable disease. Anxiety is a communicable disease. Disease is what ails people. It’s tempting to claim an absolute objectivity to scientific research, to say that an illness is the same no matter when you study it. But illnesses are very much products of their time because of how microbes change, or because of how a community reacts, or because the illness itself is a function of the community. People are at the very center of every story of disease, and if we forget that we don’t treat the illness.