by Sonia Shah
Water ballast, used in iron ships, carried cholera even more efficiently. Iron ships, besides being watertight and making water ballast possible, were faster and stronger, and had more room for storage than wooden ships. The first iron steamboat was built in 1820 and traveled from London to Le Havre, France, and then to Paris. By 1832, Europe’s iron ships steamed to Africa and India.
As a method of transporting marine organisms, writes the marine ecologist J. T. Carlton, ballast water “appears to have few if any parallels on land or at sea for its biological breadth and efficiency.”27 Modern studies suggest that ballast water carries some fifteen thousand marine species across the oceans and seas every week, cholera vibrio among them. Each one of the millions of gallons of ballast water sucked up from the shallow bays and estuaries of cholera-plagued Europe and Asia could hold some tens of billions of viruslike particles, awaiting their release across the sea.28
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By land, the interior of the United States at the time of cholera’s emergence was largely impenetrable. Most of the nation’s roads were little more than muddy tracks through wild forests and swamps, on which fallen trees and mud could strand horse-drawn carriages and carts for weeks. Transporting goods only a few dozen miles into and out of the interior of the country by land required as much time and money as shipping them across the ocean to England.29
Boats, in contrast, moved swiftly and reliably. Newly developed steamboats allowed passengers to travel up and down natural waterways such as the three-hundred-mile-long Hudson River, which ran from the Adirondack Mountains to New York City, and the two-thousand-mile Mississippi River, which flowed from northern Minnesota to the Gulf of Mexico.
But before the mid-1800s, the Appalachian Mountains’ unbroken spine of peaks down the eastern half of the country served as a gargantuan wall separating the shipping trade along the Mississippi River and the Great Lakes from the international oceangoing trade along the Hudson and the Atlantic Ocean.30 Cholera or any other waterborne pathogen that made it to U.S. shores was blocked from the waterways farther west.
The Erie Canal, which opened in 1825, changed all that, wedding the salt water of the Atlantic with the freshwater web of the interior. The canal cut right through the Appalachians, connecting the Hudson River to Lake Erie, more than three hundred miles away, at Buffalo. It was a marvel of engineering, bought for the then astronomical sum of $7 million (that’s some $130 billion in 2010 dollars), a “watery highway,” as Nathaniel Hawthorne put it, “crowded with the commerce of two worlds, till then inaccessible to each other.” By slashing transportation costs between the interior of the country and its coasts by 95 percent, the canal transformed the economy of the port at its southern terminus, New York City. Thanks to the canal, New York would eclipse its rival port cities, Philadelphia, Boston, and Charleston, becoming “a city of countless ships, which line both the banks to a considerable distance, with a forest of masts, to which few other cities can present a parallel,” as one observer put it.31
But while the canal dramatically boosted commerce, it also allowed the microbial pathogens of the rest of the world to wash into every corner of American society. To celebrate the opening of the canal, dignitaries had poured water bottled from thirteen of the world’s great rivers—the Ganges, the Nile, the Thames, the Seine, the Amazon, and others—into the swirling waters of New York harbor, along with a keg of water from the canal itself. They were celebrating the new ease of waterborne trade, but their ceremony more accurately evoked the new era of waterborne disease they’d begun.32
Traffic on the canal was intense. Narrow canal boats departed daily from even the tiniest villages along the way, running all day and night. Thirty thousand people toiled on the canal’s eighty-three locks and aqueducts and guided the horses and mules that pulled boats through its waters, whole families living along its path to ensure its daily functioning. By 1832, half a million barrels of flour and more than one hundred thousand bushels of wheat—not to mention 36 million feet of timber that year alone—had been sent down the Erie’s stagnant, shallow waters. Canal boats, piled high with logs and crammed with passengers, sometimes had to wait for as long as thirty-six hours in queues at the locks.
And along with the wheat and tea came waves of immigrants. They disembarked from schooners that crossed the Atlantic, rode along the canal, and transferred to new vessels for the continuing journey westward on the water, bringing cholera with them.33
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In the spring of 1832, tens of thousands of immigrants from cholera-plagued Europe arrived at seaports along the eastern coast of North America. Cholera first struck in Montreal and Quebec City, at the northeastern terminus of the spider’s web of rivers and canals that sprawled across North America. Over eleven brutal days, cholera killed three thousand in those two Canadian cities and started breaking out in nearby canal towns. Once cholera made it into the canal system, it had secured its ticket into the rest of the continent. Scores of soldiers from New York were heading west to fight the Native American warrior Black Hawk over disputed territory in Illinois. Cholera followed them westward like a shadow. Dozens of soldiers fell ill on the riverboats and were left behind along the way, seeding new outbreaks. Others, terrified, deserted. A passerby encountered six cholera-plagued deserters along the road between Detroit and Fort Gratiot, Michigan, at the southern tip of Lake Huron; hogs consumed the corpse of the seventh. “Some died in the woods and were devoured by wolves,” writes the cholera historian J. S. Chambers. “Others fell in the fields and along the roadside but were left untouched where they fell. The straggling survivors, with their knapsacks on their backs, and shunned as the source of a mortal pestilence, wandered they knew not whither.” Of the entire contingent, more than half died or deserted “without ever firing a shot.”
Downstream in New York City, more than seventy thousand residents panicked by the news of cholera’s arrival in North America fled.34
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Very little of the grand canal era that the Erie Canal ushered in remains today. The current state of the C&O Canal in Maryland testifies to its precipitous decline. The canal, which ferried coal from the Allegheny Mountains from 1831 to 1924, is now primarily used as a recreational area. The long ditch is mostly dry, and the old lockhouses, where lockkeepers and their families once lived, are in ruins. Only their stone foundations and their nearby water pumps remain, hidden behind scrubby pawpaw trees. Their outhouses, situated a handful of yards away, have been replaced by light blue porta potties for passing bicyclists outfitted in garish synthetic fabrics, zooming down the canal’s old towpath where mules and horses once pulled boats. The draw here, once again, is the wild, shallow, and barely navigable river, which attracts kayakers and canoeists, and the odd local kid crashing through the woods for a quick summer’s dip.35
But even as the canals fade into oblivion, the avalanche of trade and mobility that they began continues, gaining speed.
Canals and steam engines, along with coal and cotton gins and other miracles of the factory age, were the first to pry the global economy out of its historical stranglehold. For hundreds of years, world economic production had remained relatively flat, rising just 1.7 percent per capita per century, as barely fed humans scratched out a living on the meager strength of their own metabolism. Then we unleashed the buried energy of fossil fuels, sparking the Industrial Revolution. In less than a century—between 1820 and 1900—world economic production doubled. It’s continued to expand ever since. In the last sixty years, global trade has increased a whopping twentyfold, faster than population or GDP growth.36
Canals sowed the seeds of their own demise. By introducing Americans to the world of international commerce—for the first time, farmers in Buffalo could enjoy fresh Long Island oysters and exotic foreign commodities like tea and sugar—they sparked an appetite that they’d never be able to satisfy. Demand for ever faster, more powerful transportation grew like a cancer and the canals could not hope to keep up. They were, after al
l, only four feet deep. First came the railroads. Then the highways. Finally, today, the airplane—which carries global trade’s most high-value products—has eclipsed them all.
The machine invented by the Wright brothers in 1903 now carries one billion human beings through the clouds every year.37 They don’t just fly in and out of a handful of prominent airports in major cities, but into and out of tens of thousands of airports in small towns and minor cities in even the most remote and far-flung nations. There are some fifteen thousand airports in the United States, but not only that: there are also more than two hundred in the Democratic Republic of Congo, one hundred in Thailand, and, as of 2013, nearly five hundred in China.38
New York City is no longer the center of today’s global transportation network, of course. The hub has shifted. Of the ten largest and busiest airports in the world, nine are in Asia, seven in China alone.39 And just as the United States’ gateway to the world was once New York City, China’s gateway to the world is Hong Kong, where more cargo—both visible and invisible—is loaded onto airplanes than anywhere else. Whereas cholera sailed and steamed around the world, cholera’s children fly.40
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The growth of wet markets created the conditions for the SARS virus to spill over and adapt to humans, but it was the modern air travel network and a single establishment—a nondescript business hotel called the Metropole in the middle of Kowloon in Hong Kong—that distributed it across the planet, triggering the global outbreak of 2003.
SARS’s first victims in south China had been rushed to local hospitals, including the Sun Yat-Sen Memorial Hospital in Guangzhou. There, clinicians working around the clock provided whatever care they could, but they also continued living their lives. One, Dr. Liu Jianlun, finished his shift tending SARS patients, then cleaned up, changed clothes, and left Guangzhou for the ninety-mile trip south to Hong Kong to attend a wedding. A few hours later, he checked into Room 911 at the Metropole, which is where the SARS virions in his body made their escape.41
So much virus took leave of his body in that room that investigators recovered genetic evidence of the virus in the carpet months later.42 Just how SARS spread from Dr. Liu to twelve other hotel residents remains unclear. Perhaps they shared an elevator ride with him or passed through the hallway outside his room after he’d coughed or vomited. Or they touched the corridor walls after he had brushed against them with a hand he’d sneezed into. Or inhaled some of the aerosolized virus that had escaped from his room after he flushed the toilet.43
What we do know is that Liu’s fellow hotel residents were a mobile, international bunch. So were mine, when I visited the hotel (now called the Metropark) in the winter of 2012. In the dimly lit hotel bar, outfitted with a drop ceiling covered in glossy black tiles, Spanish-speaking couples quietly downed rounds of shots while a white-haired Australian browsed the business section of an English-language newspaper. A little later, I overheard him discussing his financial dealings in Tanzania and Indonesia with a trim Asian businessman.
One of Liu’s fellow residents in 2003 was a flight attendant. She made it as far as Singapore before being hospitalized, where she passed on the virus to her doctor, who planned to fly to New York, where he was to attend a medical conference. He made it as far as Frankfurt, Germany. Others exposed to Liu at the Metropole boarded planes to Singapore, Vietnam, Canada, Ireland, and the United States. Within twenty-four hours, the SARS virus from Liu had spread to five countries; ultimately, SARS appeared in thirty-two countries. Thanks to the miracle of air travel, one infected man seeded a global outbreak.44
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Many people worry about catching bugs during air travel, but in fact only a subset of pathogens easily spreads during flights themselves. Pathogens that spread via direct contact, like HIV and Ebola, are unlikely to amplify during flights. Only two Ebola-infected people are known to have traveled by air during the first year of the 2014 epidemic in West Africa, and neither of them infected anyone else on the flights themselves.45 (Contact-transmission pathogens like Ebola are much better suited to take advantage of practices like burial rituals, in which people ceremonially bathe infected corpses, and health-care settings in which clinicians extensively handle infected patients, both of which played important roles in fueling the 2014 Ebola outbreak.) Pathogens that spread between people through vectors, like mosquitoborne West Nile virus and dengue, can only occasionally survive air travel, too—the cool, arid atmosphere of modern airplanes is often deadly for their mosquito carriers.
Respiratory pathogens like SARS, however, are ideally suited. By spreading through droplets released while coughing or sneezing or through aerosols, extra-tiny droplets that can hang suspended in the air, they can turn a single infected carrier upon departure into a planeload of carriers upon arrival. A less noted but equally potent way air travel broadcasts pathogens is by extending the mobility of infected carriers who would have been far too fragile to travel via other means. Surgical patients, for example, played little role in the global spread of infectious pathogens in the past. People who’d recently undergone surgery were relatively immobile. Not so today. Surgical patients travel the world, carrying pathogens from operating rooms on one side of the globe to the other.
Every year, for example, hundreds of thousands of so-called medical tourists from the United States, Europe, the Middle East, and elsewhere fly to countries such as India to undergo surgery. Thanks to market reforms in the early 1990s, which unleashed several decades of 8 percent annual growth in the Indian economy, modern private hospitals in India now provide the same standard of care as Western hospitals. But because poverty and low wages persist in the country (among other reasons), they can do so at a fraction of the cost. As a result, foreign patients looking for an affordable organ transplant, or a knee replacement, or heart surgery, arrive in droves.46
This is a striking reversal from as recently as the 1980s, when India was still an economic backwater, and families like mine who went there to visit relatives packed their suitcases full of any medical supplies we thought we might need so we wouldn’t have to rely on spotty local health services. Locals who could afford it flew to New York or London for high-tech medical attention.
Back then, airports in Indian cities were crumbling fluorescent-lit buildings where gangs of skinny, mustached young men in tight button-down shirts hawked taxi rides, while knots of bedraggled multigenerational families clutched their tickets anxiously. One hoped not to have to use the alarmingly blocked and overflowing public toilets. Today, the New Delhi Indira Gandhi International Airport is a sparkling facility, complete with upscale cafés, gigantic, colorful abstract murals, and moving walkways ferrying trendy young business travelers and their ubiquitous tiny black gadgets. When I visited in 2012, I found signposted directions to Medanta Hospital, one of many gleaming new corporate-owned private hospitals that cater to medical tourists, conveniently located right outside the baggage claim.47
Fifteen percent of Medanta’s patients arrive from overseas for surgery, which costs them one-fifth the price they’d pay in Western countries, hospital spokespeople say. The hospital itself, a short drive from the airport, is an impressive building with expansive verdant gardens, encircled by tall wrought-iron gates that seal it from the old world that exists just beyond: hawkers selling freshly squeezed juices from fly-covered wooden carts, workers crouched on their haunches cooking over smoky fires. Inside, the hospital looks and feels like a museum, with soaring ceilings, white marble tiled floors, and giant walls of frosted glass.
Behind one frosted glass door is a special lounge reserved for medical tourists and their relatives. The only Indians here are behind the counters: the others are of East Asian, Middle Eastern, and Western ancestry, still toting their giant shrink-wrapped suitcases. They loll on black leather couches and enjoy free hot drinks while watching flat-screen televisions. The hospital’s International Patient Services team organizes their treatment packages, assists them with their visas, provides airport pic
kup, and arranges hotel reservations and postrecovery sightseeing trips. They even provide a concierge service for dining and entertainment.48
But as comfortable as these medical tourists may be, once under the knife their internal tissues will be exposed to New Delhi’s unique microbial environment, and they bring any microbes they gain during their procedures back home. People who undergo surgeries are especially vulnerable to infectious pathogens. Surgeons’ knives breach the protective layer of skin that separates the interior of the body from the exterior environment, allowing the army of microbes that live on the surface of the skin, in the air above the bed, and on the surgical instruments and other objects that pass over the open wound to slip in. Even the most elaborate sterilization practices often fail to stop them. Those that make their way into the body are likely to flourish, since the surgery itself, not to mention the conditions that often precede it, depress patients’ immune systems.
Hospitals like Medanta boast infection rates as good as or lower than those of hospitals in the United States, but the bacteria responsible for these infections are not the same. For one thing, most bacteria in Indian hospitals are gram-negative, which means they are encased in tough outer membranes that make them more resistant to antibiotics and antiseptics than the gram-positive strains that dominate in Western hospitals. (The term gets its name from Hans Christian Gram, the developer of the test that distinguishes between the two types.) For another thing, since India suffers a heavy burden from bacterial diseases—diarrhea and tuberculosis kill around a million people every year—and does not regulate the use of antibiotics (they’re widely available across the country without a prescription), many of India’s bacterial pathogens are impervious to antibiotics. Compared to about 20 percent of hospital infections in the United States, more than half of hospital infections in India are resistant to common antibiotics.49
