by Sonia Shah
Social and economic factors that contributed to a 2009 outbreak of dengue in Florida were similarly ignored. In 2008, South Florida had suffered a rash of foreclosures, which had allowed mosquitoes to breed in abandoned swimming pools and gardens out of reach of mosquito inspectors and homeowners, leading to an explosion of mosquitoes. The following year, dengue broke out for the first time in seventy years, hitting particularly hard in Key West, the epicenter of the foreclosure crisis. A CDC study found that 5 percent of the population there harbored antibodies to dengue. But biomedicine’s reductionist noncollaborative approach would hardly have led anyone to consider addressing the housing crisis as part of an appropriate response to the outbreak.78
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Since the mid-twentieth century, biomedicine has been rightly celebrated for its powerful ability to render lifesaving cures. But its limits, which have already started to show, will only become more apparent in the coming years. Some of the external disruptions that are now eclipsing microscopic mechanisms as drivers of new disease are more amorphous, wide-ranging, and unpredictable than the world has ever seen.
EIGHT
THE REVENGE OF THE SEA
If there’s any single historical development that actuated all of the various ways human activity contributes to pandemics, it’s the harnessing of fossil fuels such as coal, oil, and gas. Before the discovery of coal and oil, civilization drew its energy primarily from wood fires and human labor. To acquire more energy, society had to expend a nearly equal amount of energy, whether it was in the form of felling trees or feeding slaves. There wasn’t much of an energy surplus, which limited the size of human populations and their expansion across the globe as well as the frequency and scale of pandemics.
The discovery of rich veins of coal and buried reservoirs of oil liberated society from those thermodynamic constraints. The best fossil fuels can provide one hundred times more energy than their extraction requires.1 The energy surpluses they unleashed allowed civilization to expand at a previously unimaginable clip. Each manifestation of fossil-fueled power—whether in the form of increased agricultural yields made possible through petrofertilizers or in the speed and scale of trade and transport—contributed to the emergence and spread of pathogens. Petrofertilizers doubled agricultural yields, feeding the growth of populations and their crowding into cities. Coal powered the steamboats that carried cholera across the oceans and the canal-building machines that ferried it into the interior of continents. Oil powered the machines that cut down the forests and the airplanes that dispersed the viruses they once concealed across the globe.
But in addition to fueling the population growth, urbanization, and mobility that contribute to pandemics, the global bonfire of fossil fuels will heighten the likelihood of pandemics on its own, in a way that is likely to be even more consequential than all of its contributing factors put together. The voraciousness and speed with which we consumed fossil fuels—one hundred thousand times faster than they could form underground—assured that. It was like eating a lifetime’s supply of food at a single meal. The energy in fossil fuels, which derived from their carbon, had accumulated underground for millions of years. By digging it up and burning it, we released all of that ancient carbon into the atmosphere in a matter of decades, an outburst that would alter the climate and all the creatures that lived within its confines for generations.
By the mid-twentieth century, the concentration of carbon dioxide in the atmosphere had increased by more than 40 percent compared to preindustrial levels. Hanging in the atmosphere like a blanket, the excess carbon steadily warmed the air below, gently heating the surface waters of the ocean. Every decade, the temperature of the seas’ surface waters rose by a little over one-tenth of a degree. Newly warmed waters, sinking to the depths and splashing into planetwide flows, altered the ocean’s constitution in subtle but transformative ways, like a shot of vodka in a glass of tomato juice. Currents, fueled by the temperature gradient between cool waters moving over warm ones, were transformed. Rainfall patterns around the globe shifted, as the growing cloud of vapor that wafted above the warmer seas swelled by 5 percent. The warming waters, expanding as they heated up, lapped ever higher on coastlines and beaches, inundating freshwater habitats with salt water. By 2012, in some parts of the world, the sea had risen eight inches above 1960 levels.2
As the seas changed, so did cholera’s fortunes.
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For most of the twentieth century, cholera’s connection to the sea was unknown. The sea itself was considered a static, unchanging place, a vast expanse “of eternal calm,” as the environmental writer Rachel Carson put it, “its black recesses undisturbed by any movement of water more active than a slowly creeping current.”3 Scientists held plankton, those microscopic creatures floating in the ocean, in similar regard. Plankton, they believed, blanketed the languid seas uniformly, like a layer of dust on a mantelpiece. And it had nothing to do with cholera. Cholera vibrio, according to conventional wisdom, lived on land, traveling from one person’s gut to another via contaminated drinking water.
A mild-mannered zoologist named Alister Hardy thought otherwise. He devised a simple but ingenious little machine that would revolutionize scientific understanding of plankton. It was a long, continuously moving roller that, when towed behind a boat, unfurled a band of silk that captured samples of plankton. Since it didn’t need much by way of expert handling to install and didn’t take up much room, ships of all kinds could drag the spools of silk behind them, collecting billions of samples of plankton for scientists to analyze. (The first to do so was the Discovery, the ship that had earlier carried the explorers Robert Falcon Scott and Ernest Shackleton to the Antarctic in 1901.)4
As Hardy’s machine was dragged across the sea, cholera’s life underwater slowly came into focus. The microbiologist Rita Colwell made the unexpected discovery of Vibrio cholerae in the waters of the Chesapeake Bay in 1976.5 Although she couldn’t culture the vibrio in the lab—that is, get it to produce colonies on little plastic dishes of agar (which microbiologists considered the “gold standard” for identifying bacteria)—by exposing her samples to fluorescent antibodies that would bind to the bacterium, she could see the vibrio glowing. She knew they were there.6
So she continued to sample coastal waters for Vibrio cholerae. And everywhere she looked, she found it: in ponds, rivers, lakes, and seawater from five continents. Ultimately, Colwell and other scientists discovered more than two hundred serogroups of Vibrio cholerae that lived in the sea, including types that produced cholera toxin and types that did not. They discovered how they lived, too: in conjunction with zooplankton, especially copepods.7
Meanwhile, Hardy’s machine, now known as the Continuous Plankton Recorder, had compiled one of the most extensive and longest-running records of marine life in the world. By the beginning of the twenty-first century, it had been dragged across more than 5 million nautical miles of the North Atlantic. The spools of silk revealed that far from being dustlike and uniform, plankton are as exquisitely sensitive to their environment as the tiny trembling hairs on a spider’s leg. They responded to subtle signals in the sea and air—the temperature of the surface waters, the northern boundary of the currents of the Gulf Stream—that operated over thousands of miles of ocean.8
And the changing conditions in the North Atlantic had clearly affected them. Starting in 1948, their biomass had plummeted sixfold. Decades later, the plankton had returned, but they weren’t the same. Warm-water plankton species had shifted six hundred miles, reacting to the increasingly warm surface of the sea by moving north at the rate of fourteen miles a year.9
These shifts, in turn, dictated the fate of the cholera vibrio that lived in and on plankton. The insights revealed by Hardy’s machine, coupled with Colwell’s research, had pioneered a new understanding of the role of environmental microorganisms in shaping life on Earth. Whatever was going on with cholera had as much to do with what occurred under the waves as with what transpired in t
he lives and habits of people on land.
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After causing nearly a century of continuous pandemics, cholera had seemingly disappeared in 1926, receding into its ancestral homeland in the Bay of Bengal. “As a world scourge,” the historian William H. McNeill wrote in his landmark 1977 book on the role of infectious disease in history, cholera had been “effectively defeated.” Its demise exemplified “an unusually tidy paradigm” of “triumphant containment.”10
In fact, cholera hadn’t disappeared in 1926, exactly. The particular strain that had ravaged the world in six pandemics—now known as “classical 01” Vibrio cholerae—had died out. But before vanishing it had spawned a sneaky little descendant, one particularly well suited to exploiting new opportunities presented by the changing sea it lived in. This new kind of cholera vibrio could thrive in rivers, estuaries, lakes, and ponds at least three times longer than classical 01.11 It was a peculiarly resilient creature, able to withstand an onslaught of antibiotics, too.12
Although public-health experts did not recognize it as a pandemic-worthy pathogen until the 1970s, the descendant had first been spotted in 1904 at El Tor quarantine station on the west coast of the Sinai Peninsula, where it had been extracted from the corpses of six pilgrims to Mecca who’d died of diarrhea. At the time, compared to the cholera raging across the globe caused by classical 01, this new vibrio seemed insignificant. Investigators decided it wasn’t a cholera vibrio at all but just some other kind of generic, forgettable vibrio. They named it, simply, after the place they’d found it: El Tor vibrio.13 And then the medical establishment basically forgot about it.
El Tor vibrios resurfaced in 1937, causing outbreaks on the Spermonde archipelago, a series of isolated, low-lying coral atolls off the coast of South Sulawesi, Indonesia. Still, they escaped international attention.14 The vibrio killed 65 percent of those it infected, but since the outbreaks did not spread beyond remote Sulawesi, the global health authorities at the World Health Organization didn’t consider them to be caused by cholera. The disease that El Tor vibrios caused was just some kind of “peculiarity,” the agency said, “conditioned by local circumstances.” They called it “paracholera” and decided that nothing much should be done to contain it. “Quarantine, strict isolation of sick persons and their contacts, disinfection and mass immunization,” the WHO reported, “are not justified.”15
This would turn out to be a significant missed opportunity. For as environmental conditions in Spermonde changed, so did the nature of El Tor’s outbreaks. Over the following years, increasingly voluminous rains, more powerful storms, and rising seas pummeled Sulawesi. Every year, rainfall increased by two to three inches. Storms became so ferocious that even the experienced fishers of the islands regularly lost their boats at sea. Rising seas permanently contaminated wells with salt water.16
In 1961, El Tor “paracholera” dramatically extended its reach, striking out of Sulawesi into other parts of Indonesia as well as the Philippines, Malaysia, and Thailand. By the summer, El Tor broke out in Guangdong province in south China, where it killed between thirty thousand and fifty thousand people, Western commentators estimated. According to their reports, whole villages had been razed. From there it seeped into Hong Kong and eventually into South Asia, cholera’s heartland.17 Since it was still traveling incognito as paracholera, not real cholera, the international rules regarding quarantines and notifications that pertained to cholera didn’t apply.18
El Tor arrived in Africa, where the disease had never been seen before, in 1971.19 It struck a huge gathering that took place on the banks of Lake Chad, a freshwater lake bordered by Chad, Cameroon, Niger, and Nigeria, for the circumcision ceremony of an important sheikh. Over eight hundred sickened and more than one hundred perished in a matter of weeks. The shallow, warm, plankton-choked body of water proved an excellent home for the environmentally resilient El Tor vibrio. Thanks to a frenzy of dam building, irrigation diversions, and land clearings along its coast, the lake was well on its way to drying up. By 2000, the lake, which had once covered over ten thousand square miles, extended over fewer than six hundred square miles, with a depth of less than five feet. Regular, deadly outbreaks across the Lake Chad basin followed, year after year.20
Finally, the WHO admitted that paracholera, a supposedly mild form of cholera-like illness peculiar to specific remote locations, didn’t exist. El Tor was cholera, in all its terror-inducing, virulent glory. After four decades of “triumphant containment,” cholera was back. A seventh pandemic had begun.21
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In 1990, cholera arrived in South America, where it had not been seen since 1895.
Once again, its arrival coincided with a peculiar climatic phenomenon, in this case, El Niño Southern Oscillation, or ENSO. ENSO occurred every two to seven years, usually around December, which is why locals had named it after the baby Jesus, whose birthday they celebrated around the same time. It began when the trade winds failed, freeing the warm waters around Indonesia to drift eastward.22 That warm patch of water unleashed rain clouds into the air above it, which acted like a boulder dropped into a stream, interrupting a range of other climatic patterns around the globe, leading to dry winters in the northwestern United States, heavier rain in East Africa, and more bushfires in north Australia.23
When El Niño’s warm patch of water collided into the west coast of Peru in late 1990, it changed the composition of local plankton as well as the currents around the coast: local zooplankton populations crashed as equatorial zooplankton populations rushed in. The prevailing current, which flowed north up the coast, reversed direction.24 Any cholera vibrio in those waters would have been made more abundant, more resilient, and more deadly by its warmth. Warm water helped cholera vibrio produce the toxins that desiccated their human victims. And it helped the bacteria attach to plankton, allowing it to survive for longer and in harsher conditions.25 (Clinging to the egg sac or lining the gut of a copepod, vibrio concentrations could reach up to five thousand times higher than when free-living, and the bacteria could persist for more than a year.)26
Not long afterward, people who lived along a six-hundred-mile stretch of Peruvian coastline started falling ill with El Tor cholera.27 Public-health authorities urged Peruvians to refrain from interacting with the newly deadly waters along the coast. Police arrested street vendors selling fish, including those selling the national dish, ceviche, because it consisted of raw fish marinated in citrus.28
Nevertheless, by the spring of 1991, cholera had sickened seventy-two thousand Peruvians and had started to spread across the continent. Rivers carried cholera into Ecuador, Colombia, and Brazil, and to the border of the United States. Cholera-rich surf washed onto the beaches of Los Angeles, compelling the hit television show Baywatch to consider fleeing north of the city. Cargo ships, their holds full of cholera-rich ballast water, dumped cholera into Mobile Bay, Alabama, leading to the closure of local oyster beds. An Aerolineas Argentinas flight carried cholera from Buenos Aires to Los Angeles, in the cholera-laced shrimp salad it fed to its passengers, sickening several dozen and killing one. Cocaine smugglers brought it into the remote southern Mexico villages where they stashed their secret airstrips.29
By 1993, nearly a million had sickened across Latin America, and some nine thousand were dead. Only Uruguay and the Caribbean had escaped El Tor cholera’s fury. But not for long.30
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With El Tor cholera increasingly abundant in the environment, by 1994 it had picked up a new trick, possibly by acquiring genes from its predecessor: the ability to secrete the same kinds of killer toxins that classical 01 had in the nineteenth century. Now, in addition to being more resilient in the environment and tougher against antibiotics than its predecessor, El Tor would be as efficient a killer as classical 01 had been.31
In Africa and Asia, El Tor’s new toxin-producing ways ratcheted the death toll upward. Between 2001 and 2006, the proportion of cases in which it caused life-threatening dehydration rose from 30 to near
ly 80 percent.32 In 2007, “altered” El Tor had become the dominant cholera strain in South Asia, including in Nepal. Three years later, a group of soldiers hired by the United Nations escaped a local outbreak and boarded planes en route to the mountainous, earthquake-damaged island of Hispaniola, altered El Tor burning in their bellies.33
Haiti was a ticking bomb for a cholera explosion, but not just because of its history of strife, poverty, and deficient sanitation. Environmental conditions conspired to welcome cholera vibrio, too.
Up until 2010, pathogen-rich Haiti had been strangely immune to cholera. Cholera had first arrived in the Caribbean in 1833, with an outbreak in Cuba. But while the disease spread over the region, including the Dominican Republic, which occupied the eastern two-thirds of Hispaniola, there is no historical record of the disease showing up in Haiti. The Haitian historian Thomas Madiou speculated in the late 1850s that something peculiar about Haiti’s geography protected it—“some emanations of our soil that don’t allow cholera toxins to survive,” he wrote, or “some condition of our atmosphere.” If so, that protection vanished in the wake of the magnitude 7.0 earthquake that hit in January 2010.34 Silt and limestone washed into the rivers, creating the kind of high-nutrient, alkaline conditions that vibrios love. The traumatized population was even more malnourished and poorly housed than they had been before. “There were very unnatural conditions in Haiti because of the earthquake,” says the cholera expert Anwar Huq. “Nutrients came out of the ground. The ecology changed.”35 Ten months later, cholera finally annexed Haiti.36
The seventh pandemic, fueled by the most wily, resilient, and deadly cholera strain the world had ever seen, would be the longest and most widespread cholera pandemic ever. It continues to this day.37