Pandemic: Tracking Contagions, from Cholera to Coronaviruses and Beyond

by Sonia Shah

Such was the fate of a passenger ahead of me in line for Spirit Air Flight 952, from Port-au-Prince, Haiti, to Fort Lauderdale, Florida, in the summer of 2013.

pathogen,

Cholera is one of only a handful of pathogens—including bubonic plague, influenza, smallpox, and HIV—that in modern times have been able to cause pandemics, contagions that spread widely among human populations.

In the nineteenth century, cholera struck the most modern, prosperous cities in the world, killing rich and poor alike, from Paris and London to New York City and New Orleans. In 1836, it felled King Charles X in Italy; in 1849, President James Polk in New Orleans; in 1893, the composer Pyotr Ilyich Tchaikovsky in St. Petersburg. Over the course of the nineteenth century, cholera sickened hundreds of millions, killing more than half of its victims. It

The crowded and unsanitary conditions of rapidly growing cities allowed the bacteria to efficiently infect scores at a time.

It took nearly a hundred years of deadly cholera pandemics for cities like New York, Paris, and London to rise to cholera’s provocations. To do it, they had to remake the way they housed themselves, managed their drinking water and their waste, governed the public’s health, conducted international relations, and understood the science of health and disease.

2 “To write about infectious disease,” he added in 1962, “is almost to write of something that has passed into history.”

As societies prospered, their disease profile shifted. Instead of being plagued by contagion, they suffered primarily from slow-moving, chronic, noncommunicable conditions, like heart disease and cancer.

shared latrines,

In the American towns where we lived, where drinking-water supplies had been cleaned up; sewage contained, treated, and distantly disposed of; and a public-health infrastructure built, infectious diseases were a problem that had been solved.

writ large,

Besides HIV, there was West Nile virus, SARS, Ebola, and new kinds of avian influenzas that could infect humans.

Newly rejuvenated microbes learned to circumvent the medications we’d used to hold them in check:

All told, between 1940 and 2004, more than three hundred infectious diseases either newly emerged or reemerged in places and in popula...

virologist Stephen Morse admits to having considered the possibility that these strange new creatures hailed from outer space:

the demise of infectious diseases in developed societies had been “greatly exaggerated.”

the mental illnesses that we’d once chalked up to lifestyle and genetics were actually the work of other untamed microbes.

Many experts believe that a cholera-like pandemic looms. In a survey by the epidemiologist Larry Brilliant, 90 percent of epidemiologists said that a pandemic that will sicken 1 billion, kill up to 165 million, and trigger a global recession that could cost up to $3 trillion would occur sometime in the next two generations.

The Ebola virus broke out in a remote forest village in Guinea in early 2014. It would have been easy to contain using only the simplest, cheapest measures had it been squelched early on at its source. Instead, the virus, which had previously infected no more than a few hundred people at a time, in a single year spread into five neighboring countries, infected more than twenty-six thousand people, and would cost billions to contain.

although more than half a million others around the world died of H1N1

there’s an inherent paradox: the

By telling the stories of new pathogens through the lens of a historical pandemic, I could show both how new pathogens emerge and spread, and how a pathogen that had used the same pathways had already caused a pandemic. The path from microbe to pandemic would be illuminated in the overlap, where two dim beams intersected.

the wet markets of south China,

Wet markets are open-air street markets where vendors sell live animals captured from the wild to consumers to slaughter and consume.

they’re responsible for about 15 percent of all cases of the common cold.)

The percentage cronavirus responsible for

From the horseshoe bats, it had spread into other wild animals caged nearby, including raccoon dogs, ferret badgers, snakes, and palm civets. As the virus spread, it mutated.

the virus colonized the cells lining the respiratory tract.

pneumonia

The SARS virus vanished after that. Like a brightly burning star, it used up all its available fuel, killing people too quickly to spread any farther.

He laughed mirthlessly.

As we turned the corner, the smell hit first, pungent, musky, and damp. The wet market consisted of a series of garage-like stalls lining a cement walkway. Some had been fashioned into office-cum-bedroom-cum-kitchens, in which the animal traders, bundled up for the weather, were passing the time waiting for customers. In one stall, three middle-aged men and a woman played cards on a folding table; in another, a bored-looking teenage girl watched a television bolted to the wall. As we walked in, a man flung the dregs of his soup bowl into the shallow gutter between the stalls and the walkway, a family of eight huddled around steaming bowls of hot pot behind him. A few minutes later, he reappeared to vigorously blow his nose into it.

The fact that the virus had spread from bats into civet cats had been especially critical to SARS’s emergence. The civet cats were, for some reason, especially vulnerable to the virus.

With increased replication came increased opportunities to mutate and evolve, to the extent that it evolved from a microbe that inhabited horseshoe bats to one that could infect humans.

Were it not for them, copepods’ mountain of exoskeletons would starve the ocean of carbon and nitrogen.6

But then, in the 1760s, the East India Company took over Bengal and with it the Sundarbans.

This intimate contact allowed Vibrio cholerae to “spill over” or “jump” into our bodies.

zoonotic pathogen and one that has crossed the threshold to become a human one.

The vibrio’s toxin altered the biochemistry of the human intestines such that the organ’s normal function reversed.

Within hours, cholera’s first victims were being drained alive, each expelling more than fifteen quarts of milky-white liquid stool a day, filling the Sundarbans’ streams and waste pits with excreta.

Within a matter of months, the new plague held nearly two hundred thousand square miles of Bengal in its grip.15 Cholera had made its debut.

And yet that’s not how most new pathogens are born, because their entry into our bodies is not random.

such as malaria, ferried from the bodies of our fellow primates into ours by blood-sucking mosquitoes.

historically we are victim to some animals’ microbes more than others.

It’s also why so many human pathogens date back to the dawn of agriculture ten thousand years ago,

From cows, we got measles and tuberculosis; from pigs, pertussis; from ducks, influenza.17

into humans (and vice versa)

it’s historically been a rather slow process. Not anymore.

Such virulence was considered self-defeating: if a pathogen killed too fast or too many of its victims, there’d be none left for it to subsist upon.

As wetlands were paved over and forests were felled, different species came into novel, prolonged contact with each other, allowing animal microbes to spill over into human bodies.

The road from animal microbe to human pathogen was turning into a highway.