by Sonia Shah
Slifka liked this story, I think, for the irony of a veterinarian innocently manufacturing a deadly bioweapon. But monkeypox would never have been able to leap out of the jungles of Ghana and into little Chewy’s body had it not been for commercial air travel, which gave the pathogen its wings and the free ride it needed to disseminate itself across the globe. The flights that ferried that crate of monkeypox-infested rodents into the United States also brought Pseudogymnoascus destructans, a fungus from Europe, into New York. The fungus, which likely hitched a ride from deep inside European bat caves into American ones on the muddy boots of spelunkers, invades and digests the skin of bats. Between 2006 and 2012, the disease it causes, white-nose syndrome, has killed millions of bats in sixteen U.S. states and four Canadian provinces, leading to population declines of up to 80 percent.4
Air travel doesn’t just ferry new pathogens around; it also dictates the shape and spread of the pandemics they can cause. If you plot a modern pandemic of influenza on a map of the world as the theoretical physicist Dirk Brockmann did in 2013, the pattern will be chaotic and formless. Disease might first erupt in mainland China and Hong Kong, then randomly skip all the way over to Europe and North America with no stops in between, just as a monkeypox outbreak that started in Ghana might next appear in an animal distribution center in Texas. There’s seemingly no pattern to explain the spread, or where in the world the pathogen might skip to next.
But Brockmann found that if you track that same pandemic on a map that plots locales in terms of their proximity via air travel, a revealing picture takes shape. On such a map, New York City is closer to London, England, over three thousand miles away, than to Providence, Rhode Island, just three hundred miles away, because of the availability of direct flights. Plotting the spread of a pandemic on a flight-time map does not result in the chaotic eruptions seen on a geographic map. The pandemic resolves into a series of waves, radiating outward one by one like the ripples of a stone dropped into a lake. Our transportation network, Brockmann’s map shows, shapes the pandemic more than our physical geography.5
* * *
Cholera could never have caused pandemics without the new modes of transport developed in the nineteenth century. On the eve of cholera’s debut on the international stage, travel by sea had just started to remake the industrial world, with rapid sailboats and steamers crisscrossing oceans, and newly built canals ferrying people and commodities deep into the interior of nations. We couldn’t have devised a better transit system for a waterborne pathogen like Vibrio cholerae if we’d tried.
One might think that a marine creature like Vibrio cholerae, with access to the ocean, could make its way to almost any shore. The ocean’s waters, after all, are connected and in constant circulation. And the second-fastest ocean current in the world—the Agulhas Current—carries water from cholera’s home in the southwest Indian Ocean straight to the southern tip of Africa, at the threshold of the Atlantic.6 Surely a few pioneering vibrio-infested copepods could get swept into its stream and make their way out of South Asia.
But in fact, cholera vibrios, under their own locomotion, are nearly stationary. More than 75 percent of the copepod species they live in and on tend to stay put in the shallow surface waters in which they evolved. The few that might catch a ride on an ocean current are quickly crushed by the deep waters of the open ocean, the marine equivalent of the Sahara, where sustenance is dangerously scarce and progress slow.7
Humans can carry the microbe, of course, but only so far. A cholera victim is indeed a walking broadcaster of the bug, spewing the vibrio in his or her stool and on stool-contaminated hands and personal items. But cholera’s tenure in the human body is short, about a week at most, provided the vibrio doesn’t kill its victim before that. In the nineteenth century, when cholera first emerged, that was hardly enough time to cover the nearly five thousand miles between the Sundarbans and, say, densely populated Europe.
To make the overland crossing, cholera would require large numbers of people moving together. An army of susceptible victims sequentially infected could extend the vibrio’s viability over time and miles. This form of travel, from the perspective of the pathogen, would have made for halting progress. If too many people sickened at once, the bug could die out, with all of its potential carriers rendered dead or immune. But at the same time, if only a few fell ill, the pathogen’s chances of sequentially infecting enough travelers to carry it over the long haul diminished.
And even that would get the vibrio across only the landmasses of the Old World. To ignite a global pandemic, cholera would have to unlock access to the New World and its bustling nineteenth-century populations of susceptible settlers, slaves, and natives. Cholera would have to cross the deep waters of the ocean. Someone—or something—would have to carry it.
* * *
Europeans and Americans felt that cholera, as a disease of backward Orientals, would never reach the enlightened West. Cholera was an “exotic production … developed in the uncultivated, arid plains of Asia,” an 1831 French tome declared. They pointedly referred to it as the “Asiatic” cholera to differentiate it from their ordinary diarrhea, which they called “cholera morbus.”8
France, for example, had little to fear: “In no country but England are the rules of hygiene more faithfully observed,” one French commentator proudly opined.9 Paris, where the wealthy enjoyed airy courtyards and marbled baths in perfumed water, was nothing like the swampy, mangrove-covered Sundarbans.10 On the contrary, Paris was the center of the Enlightenment. Students of medicine from around the world descended upon the city’s new hospitals to learn the latest techniques and discoveries from leading French physicians.11
And yet, slowly but surely, cholera arrived on Europe’s doorstep. By the fall of 1817, cholera had traveled sixteen hundred miles upstream on the Ganges, killing five thousand at a military camp. By 1824, cholera had radiated into China and Persia, before freezing out in Russia that winter. A second outbreak began in India a few years later. In 1827, British troops invaded Punjab; in 1830, Russian soldiers marched off to occupy Poland. Cholera followed them like a shadow.12
Cholera took hold of Paris in late March 1832. Without the benefit of modern medicine, it killed one-half of those whom it infected, causing a set of uniquely horrifying symptoms. There was no tragic tubercular cough or romantic malarial fever. Within hours, cholera’s dehydrating effect shriveled victims’ faces, wrinkling skin and hollowing cheeks, drying up tear ducts. Fluid blood turned tarry, clotting in the bloodstream. Muscles, deprived of oxygen, shuddered so violently that they sometimes tore. As the organs collapsed in turn, victims fell into acute shock, all the while fully conscious and expelling massive amounts of liquid stool.13
Mythic tales circulated of people who sat down to dinner and died by dessert; men who returned home from work to find a note on the door saying that the wife and family lay dying in the hospital; people riding the train suddenly collapsed in front of their fellow passengers.14 And they did not just clutch their hearts and crumple to the floor, either; their bowels released uncontrollable floods. Cholera was humiliating, uncivilized, an affront to nineteenth-century sensibilities. This exotic invader, the historian Richard Evans writes, transformed enlightened Europeans into a race of savages.15
“The thought that one might oneself suddenly be seized with an uncontrollable, massive attack of diarrhoea in a tram, in a restaurant, or on the street, in the presence of scores or hundreds of respectable people,” Evans writes, “must have been almost as terrifying as the thought of death itself.”16 Indeed, perhaps more so.
One of the many abiding fears cholera inflamed was of premature burial. Today, we have monitors that beep and buzz when our vital organs fail, and, except for a few headline-grabbing cases, the gray area between life and death is pretty narrow. In the nineteenth century, that gray band was much wider, and stories of exhumed bodies buried in neat shrouds later discovered in contorted positions, bones broken, skeletal hands wrapped in torn-ou
t hair, filled newspapers and magazines, evidence of epic chthonic struggles.
Physicians had been arguing for centuries over the precise symptoms of death, and about the differences between what they called “apparent” and “real” death. In 1740, the prominent French physician Jean-Jacques Winslow had argued that some of the common tests for death—pinpricks and surgical incisions—lacked a certain precision. (Poor Winslow himself had been mistakenly declared dead and boxed in a coffin twice as a child.) Some said that the most reliable sign of death was the putrefaction of the body. But that was a stringent and stinky test for the bereaved, who might be compelled to wait around for the decay of their loved one before mourning. And even then, some argued, the corpse might still be alive, simply comatose and gangrenous.
New laws, inventions, and methods of coping with dead, or apparently dead, bodies helped diminish the problem. In the 1790s, a new system implemented at Paris mortuaries required that corpses be outfitted with special gloves, such that if a corpse’s finger so much as trembled, a string would be pulled and a large hammer would slam down on an alarm. Guards patrolled the mortuary under the direction of local physicians, ears peeled. (Today, we surveil the living for signs of death; back then, they surveilled the dead for signs of life.) An 1803 law required a day’s delay between an apparent death and the subsequent burial, just in case someone got it wrong. In 1819, the French physician René-Théophile-Hyacinthe Laënnec developed the stethoscope, which made audible even the sound of a faintly beating heart (simultaneously freeing gallant physicians from suggestively pressing their ears to their female patients’ chests). Charity groups such as the Royal Humane Society formed, for the express purpose of resuscitating the drowned, launching public awareness campaigns on the finer distinctions between the living and the dead. (Their motto, which they’ve kept to this day, is Lateat scintillula forsan, “A small spark may perhaps lie hid.”)17
Cholera terrified Parisians by destroying these few safeguards. Cholera could easily make a living person look like a corpse: blue, sunken, still. “It is so easy to be completely mistaken,” one physician complained during the 1832 cholera outbreak, “that I once marked down as dead an individual who in fact died only several hours later.”18 And yet during the epidemic, burial-delay rules were overturned. Dead bodies—along with apparently dead bodies—were piled onto rickety wagons like so much freight, occasionally spilling their contents onto the streets. All were summarily buried in mass graves, layered three bodies thick.
Local authorities outlawed public gatherings and banned markets within the city center. They marked victims’ homes, quarantining survivors inside. Still, the funeral parades continued. The churches were hung in black. The city’s hospitals overflowed with perfectly still patients on the edge of death, their skin turned shockingly purple by cholera’s depredations. Still-alive cholera patients anesthetized themselves with alcoholic punch passed off as medicine. “It was a fiendish sight,” the visiting American journalist N. P. Willis wrote. “They were sitting up, and reaching from one bed to the other, and with their still pallid faces and blue lips, and the hospital dress of white, they looked like so many carousing corpses.” Spattered blood and bodily fluids leaked from wagons carrying the dead along the city’s cobblestone roads.
In the evenings during that terrible spring, Paris’s elite attended elaborate masquerade parties where, in denial and defiance of cholera’s toll, they danced to “cholera waltzes,” costumed as the ghoulish corpses many would soon become. Willis, who attended one of the so-called cholera balls, described a man dressed as cholera itself, with “skeleton armor, bloodshot eyes, and other horrible appurtenances of a walking pestilence.” Every now and then, one of the revelers would rip off his mask, face purpled, and collapse. Cholera killed them so fast they went to their graves still clothed in their costumes.19 (Paris’s cholera balls, and Willis’s reporting on them, inspired a mordant thirty-three-year-old writer in Baltimore—Edgar Allan Poe—to pen “Masque of the Red Death,” a short story about a masquerade ball in which the entry of a masked figure “shrouded from head to foot in the habiliments of the grave” leads to the death of “revellers in the blood-bedewed halls of their revel.”)
By the middle of April, cholera had killed more than seven thousand Parisians. The final death count remains obscure. To reduce panic, the government stopped publishing death statistics altogether.20
Those who could fled the city, leaving behind a collapsed society in which cholera could rage undeterred by the ministrations of nurses, doctors, or police officers.21 “Cholera! Cholera! It is now the only topic,” bemoaned Willis. “People walk the streets with camphor bags and vinaigrettes at their nostrils—there is a universal terror in all classes, and a general flight of all who can afford to get away.” Some fifty thousand panicked Parisians decamped, a swarming exodus that spilled over the roads, rivers, and seas, carrying cholera to new lands even more efficiently than the hordes of sailors, traders, and soldiers had before them.22
They escaped on foot, they boarded carriages, they paddled downstream, and they boarded oceangoing vessels. Thanks to new trade routes, they quickly brought cholera across the sea and deep into the interior of North America.
* * *
For centuries after Columbus, crossing the Atlantic had been risky and only sporadically attempted. The Dutch, who settled what would become New York City, chartered ships to cross the ocean only once a year, if that. The difficult and costly passage took eight weeks, in part because cautious captains steered clear of the shortest route over the forbidding North Atlantic. During the British colonial era, restrictive tariffs and the predations of pirates strangled the aspirations of those shipowners who hoped to ferry goods and people across the Atlantic, quieting the ports of New York, Boston, and Philadelphia. Even after Americans gained independence from Britain, the only way to get oneself across the Atlantic was to wait for a local shipowner to advertise a date of departure and then hope that sufficient cargo and other passengers would sign up, too, and then, if all of those stars aligned, languish in a port city, often for a week or more, for the wind and weather to cooperate.
The shipping trade out of the United States started to pick up during the Napoleonic Wars, as the ports of New York, Boston, and Philadelphia captured a slice of the lucrative seagoing trade with China while Europe roiled. In 1817, just as cholera emerged in the Sundarbans, ambitious American shipowners, financed by the newly established Bank of the Manhattan Company (later to become the multinational behemoth JPMorgan Chase), established something novel in transatlantic shipping: regular scheduled service between American ports and those in Europe, including Liverpool, London, and Le Havre. No more waiting around at the docks. The sailing packets, as they were called—the Black Ball Line, the Cunard Line, and others—set sail weekly from the United States, loaded with passengers, sacks of mail, and other commodities to ferry to and fro across the ocean.23
During all of the seventeenth and eighteenth centuries, only some four hundred thousand emigrants from Europe had made it to the New World. In less than a century after the introduction of the transatlantic sailing packets, 30 million Europeans boarded ships bound for the United States. The Atlantic, once a formidable ecological barrier to cholera’s spread, had become a veritable thoroughfare for people, cargo, and the invisible microbes they unknowingly carried with them.
* * *
Infected passengers aboard the packets easily passed the vibrio to the uninfected. While first-class passengers enjoyed stylish quarters and elaborate meals, most passengers at sea traveled cheek by jowl in steerage, their unwashed hands and bodies pressed tight together. At night and during bad weather, the hatches had to be closed, trapping steerage passengers belowdecks in the dank, heavy air. “How can a steerage passenger remember that he is a human being when he must first pick the worms from his food,” one journalist who made the journey complained, “and eat in his stuffy, stinking bunk, or in the hot and fetid atmosphere of a compartment
where 150 men sleep?” Several hundred passengers might have access to just a handful of toilets, and excreta, mingled with stinking bilge water, trickled through the decks.24
Shipboard practices themselves could introduce cholera to passengers. Before setting sail, ships often filled their drinking-water casks from the same streams and bays in which local people bathed and defecated. If cholera had struck any of the port towns and cities from which ships departed or visited en route, a few local vibrios could easily be sucked up into the drinking-water supplies aboard. This water was then carried across the sea in wooden casks and tanks that were rarely, if ever, cleaned. Transatlantic passengers both drank and cooked with that water during the journey.25
Once cholera struck the passengers, the entire ship became a roving disseminator of cholera vibrio, depositing contaminated excreta directly into the seas, bays, and harbors through which they passed.26
The ships could by themselves ferry cholera vibrio, too, even if passengers aboard remained unscathed. Nineteenth-century ships carried all manner of mammals, birds, plants, and other creatures as witting and unwitting cargo. Livestock, companion animals, and pests skittered aboard. Barnacles, mollusks, algae, and other marine creatures vulnerable to colonization by cholera vibrio bored into and attached themselves to ships’ wooden hulls, making possible passages that would never have been accomplished of their own accord. (Sphaeroma terebrans, a tiny crustacean that burrows into the root tips of mangrove trees, was one such hanger-on. It bored into a wooden ship hull sometime in the 1870s and made its way from its Indian Ocean home to the Atlantic, where it now abounds, munching on the roots of mangrove trees in Florida and elsewhere.)
Ships spread thousands of species around the world in their ballast, heavy materials used to fill an empty ship’s holds to keep it stable in the water. Wooden vessels used dry ballast—tons of sand, soil, and stone—alive with crab, shrimp, jellyfish, sea anemones, sea grasses, and algae, among other creatures. They’d shovel it aboard when they left shore and dump it miles later upon reaching their destinations, creating massive deposits full of alien invaders. A few cholera-vibrio-infested crustaceans, dumped overboard in a pile of dry ballast, could seed a new immigrant colony across an ocean.
