How Scared Should I Be of a Contagious Disease Wiping Out Humanity?

In the column "How Scared Should I Be?" VICE staff writer and generalized anxiety disorder sufferer Mike Pearl seeks to quantify the scariness of the world we live in. We hope it helps you to more wisely allocate that most precious of natural resources: your fear.

Late last month, the United Nations issued a warning about global pandemics in a report so urgent, it arrived with the words "ADVANCED UNEDITED COPY" stamped on it. The document itself is 95 pages of white-knuckle terror, scolding every government on earth for complacency, and warning us that without vast improvements to worldwide public health infrastructure "the emergence of a highly pathogenic influenza virus, which could rapidly result in millions of deaths and cause major social, economic and political disruption, is not an unlikely scenario."

The UN report includes a reference to some findings from last year by the Institute for Disease Modeling, which showed that a resurgence of the 1918 Spanish flu could kill 33 million people in under nine months. Last spring, that research was briefly touted by Bill Gates, the guy who funded it, in an attempt to bring the issue of pandemics to the world's attention.

But this new report comes at a time when the virus currently scaring everyone isn't influenza, but Zika fever, an outbreak that has caused few fatalities, but has other terrifying effects including the dreaded microcephaly—babies born with abnormally small heads and undeveloped brains (something science only linked to the Zika virus last year). It may not be a deadly flu, but the rapid and seemingly unstoppable propagation of the Zika virus is drawing attention to just how ill-prepared humanity is for a novel health menace.

So is Bill Gates actually understating the risk? Could something worse than Spanish flu—deadlier and more transmissible—be biding its time on some vampire bat's fangs, one bite away from patient zero's bloodstream? What makes contagions into pandemics? And how likely is it to happen to humans?

"There are some worst-case scenarios: The stuff of science fiction, of movies like Outbreak," Stephen Morse, director of the infectious disease epidemiology program at Columbia University told me. These worst-case scenarios muddle the issue a bit.

Morse pointed out that when screenwriters need a pandemic to work on the silver screen, they often have to pull shenanigans in two ways: They come up with an altogether new virus—maybe from space—with previously unknown lethal properties, and then they have to "find some way to really make it highly transmissible," and that kind of transmissibility is "extremely rare."

Transmissibility is a challenge for some of the world's deadliest viruses. Outside of influenza's various forms, the Black Death, which wiped out perhaps 60 percent of the people in Europe, is "probably among the worst scenarios we can think of," according to Morse. "HIV took much longer to go around the world, and wasn't nearly as dramatic," he added. HIV and the Black Death have something in common: They generally aren't airborne.

With plague, that's not always the case. "In about 10–20 percent—it varies—of the people who get the classic bubonic plague, it'll go to the lungs, and then it can spread via the respiratory route, sort of like TB," Morse said. Plague that gets into your respiratory system is known as pneumonic plague. "That's usually what really kicks off an epidemic: One of those unlucky people happens to get the infection in their lungs." That example points to one of the scariest things about pathogens: Sometimes—as we're seeing with the surprise effects of Zika—they behave in ways we don't expect.

Surprise effects turn out to be a bigger danger than entirely new pathogens. "We organized a conference at the National Institutes of Health in 1989 to investigate that. Turns out, all the known [outbreaks]—with the exception of influenza sometimes—are not the result of some new evolutionary event that suddenly happens, but the result of some already-existing pathogen finding its way into the human population, and essentially trying out its chances," Morse said.

But is there precedent for something like a virus entering a population and almost completely wiping it out? "There have been cases with other species where this has happened," Morse said. He pointed to the example of the Florida panther, a species brought to the very brink of extinction—there were only six left—and the cause he pointed to was a disease called feline infectious peritonitis.

The panther isn't the only species thought to be that unlucky. Ross MacPhee, a researcher at the American Museum of Natural History, theorizes that some kind of superinfection is largely responsible for the extinction of the wooly mammoth. MacPhee also wrote a paper on a specific rat population that was 100 percent wiped out by a form of plague.

But the point is that even with known pathogens, it's not changes in their DNA, but changes in their relationships with the species they infect that can bring about such deadly outbreaks. With humans, "anthropogenic changes" he called them, happen when populations shift internally or use land differently. These new arrangements of humans provide better "feeding grounds for the pathogenic population," and to top it off, we're nowhere near a reliable system for figuring out what changes to avoid, or knowing when we've crossed a line into vulnerability.

"Once it's in the human population, you can try to estimate the trajectory, but it's very hard to know what's coming," Morse said.

The WHO wants to create a global network of early warning systems for outbreaks. Mobilization of resources to quarantine and stop an outbreak seems technologically possible, but the global community still responds sluggishly to a crisis, something we realized in retrospect as the 2014 Ebola disaster wound down. As the recent UN report noted, early warning systems have only been established by one-third of UN countries. Which makes them pretty useless.

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