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From The Unreality of Memory, which will be published in August by Farrar, Straus and Giroux. 

Viruses and bacteria hijack our minds; they make us act weirdly. For example, Toxoplasma gondii, a parasite found in cat feces, makes mice less afraid of cats; this is an evolutionary strategy, making it easier for the parasite to get from the mouse to the cat. When it spreads to humans, it may increase their risk-taking. One study found that people with toxoplasmosis, the infection caused by the parasite, “are more likely to major in business.” An NBC News story suggested optimistically that the parasite “may give people the courage they need to become entrepreneurs.”

That would be an extreme case of a microscopic parasite altering the course of our lives. But viruses and bacteria influence our everyday behavior as well. A 2010 study, for example, found that people became more sociable in the forty-eight hours after exposure to the flu virus, a period in which one is contagious but asymptomatic. The infected hosts, researchers noted, were significantly more likely to head out to bars and parties. One of the strangest of these virus-induced behavioral changes is hydrophobia, a symptom of classic rabies, also known as furious rabies. That’s not an exaggeration: people and animals infected with rabies become morbidly terrified of water. Or perhaps more accurately, they’re of two minds about water: they both want it and can’t stand the thought or sight of it. Why does this apparent biological death drive arise? It’s not so that people will die of thirst. The virus’s goal is not to kill humans—though it does do that—but to spread through our saliva, which would be diluted by drinking water.

Rabies—like toxoplasmosis, malaria, Zika, typhus, the bubonic plague, and all flus—is a zoonosis, a disease that can make the leap from animal to human. That transmission is called spillover. In his book Ebola, published in 2014, David Quammen describes “zoonosis” as “a word of the future”—one that will see heavy use in the twenty-first century. Infectious diseases persist when they have a reservoir host. We were able to eradicate smallpox, Quammen notes, because it’s not a zoonosis; it infects only humans, and once we’ve cured them, it has nowhere else to hide. Viral infections like flus, on the other hand, will continue to influence our behavior for many years to come.

Of course, one needn’t be infected with a virus to be influenced by it. In 2018, archaeologists found an unopened sarcophagus in Alexandria, and some people on social media speculated that the tomb might contain a deadly virus or bacterium—after all, when King Tut’s tomb was opened, in 1922, a number of people associated with the excavation died. “I’m pinning all my hopes on the creature in the sarcophagus,” one woman tweeted. Another wrote:

2012: oh no Mayan calendar says the world might end and we could all die

2018: PLEASE let the black Egyptian sarcophagus carry a curse that will collectively put us out of our misery

Today, whenever a story about the threat of an extinction-level event, such as an asteroid or comet headed for Earth, is making the rounds, a subset of people inevitably quote-tweet it to add something like, “Finally, some good news!” In the age of the horrible twenty-four-hour news cycle, we understand this impulse: death represents a kind of escape. But I wonder: Is this posturing really about wanting to escape, or is it about wanting to suffer?

During the black death in fourteenth-century Europe, bands of flagellants roamed from town to town, like a traveling theater troupe, putting on public performances of violent self-punishment. They would flog themselves with leather-and-iron whips while crying out to God, “Spare us!” As the historian Barbara Tuchman writes in A Distant Mirror, “The flagellants saw themselves as redeemers who, by reenacting the scourging of Christ upon their own bodies and making the blood flow, would atone for human wickedness and earn another chance for mankind.”

If the plague had been sent to punish people for their sins—Matteo Villani, a fourteenth-century historian, compared it to the great flood “in ultimate purpose”—you might think that the period following it would be one of great austerity. If anything, it was the opposite. Survivors of the plague did not become ascetic. Instead, they may have sensed a baffling meaninglessness to their being spared—survivor’s guilt being a kind of miserable apprehension of one’s own good luck. “If the purpose had been to shake man from his sinful ways,” Tuchman writes, “it had failed.” People embraced “a more disordered and shameful life,” and “behavior grew more reckless and callous, as it often does after a period of violence and suffering.” Not much had changed, according to Tuchman, though an estimated 30 to 50 percent of the European population had died:

What was the human condition after the plague? Exhausted by deaths and sorrows and the morbid excesses of fear and hate, it ought to have shown some profound effects, but no radical change was immediately visible. The persistence of the normal is strong.

A Distant Mirror, published in 1978, was so named because Tuchman felt that the awfulness of the fourteenth century—for years, she says, historians tended “to skirt the century because it could not be made to fit into a pattern of human progress”—had clear parallels to the twentieth century.

Before the current pandemic, experts had long predicted that the most likely cause of a future pandemic would be some version of the flu; flus are common, highly contagious, and especially dangerous when there’s a new strain to which people have limited immunity. Anthony Fauci, the director of the National Institute of Allergy and Infectious Diseases, has said that “in some respects, vaccines are the victims of their own success”—meaning that, although they can almost eliminate an infectious disease, it stops seeming like a threat once people stop dying. They get lax about it. “Folly is a child of power,” Tuchman writes elsewhere—the result of feeling invincible. We make stupid decisions because we think we’re indestructible. I almost fear we are. Even if we don’t succumb to any of the worst doomsday scenarios involved in climate change, the climate is certain to get worse and become less hospitable to humans in the short term. A lot of people, especially near coasts, near the equator, and in poverty-stricken areas, will be displaced, will suffer, and will die. But some of us will remain, and face a very different reality.

There’s some evidence that the reduced population and reforestation after the black death helped trigger the Little Ice Age; that wasn’t any fun for the survivors, considering it led to famine. But if there is another great mortality, it might have a tiny upside in the long view of history: a pandemic, an asteroid, or a nuclear war could all lead to global cooling.

When you look at it that way, it’s almost as though we are acting with a higher collective intelligence, employing folly as a strategy. But perhaps it’s too generous to call it intelligence. We don’t know what we want, or what purpose we serve.

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