Spillover

by David Quammen

  Once finished, with the blood and organs preserved, Aleksei dropped the carcass into a Ziploc bag. He added the other bat carcass, after dissection, to the same bag. Where do those go? I asked. He pointed to a biohazardous waste box, specially designed for accepting suspect materials.

  “But if they were food,” he added, “they’d go there,” indicating an ordinary trash basket against the wall. It was a shrug back toward our dinner discussions and the tangled matter of categorical lines: edible animals versus sacrosanct animals, safe animals versus infected animals, dangerous offal versus garbage. His point again was that such lines of division, especially in southern China, are arbitrarily and imperfectly drawn.

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  Several days later we traveled down to the city of Lipu, about seventy miles south of Guilin, to visit a rat farm that interested Aleksei. The trip took two hours on a rather luxurious bus—one offering seat belts and bottled water. At the bus station in Lipu, while waiting for our local contact to arrive, I noticed a sign stipulating security restrictions. The sign was in traditional Chinese characters but I could tell from the illustrations what was disallowed on board Lipu–Guilin busses: no bombs, no fireworks, no gasoline, no alcohol, no knives, and no snakes. We weren’t carrying any.

  Mr. Wei Shangzheng eventually pulled up in a white van. He was a short, stocky, amiable man who laughed easily and often, especially after his own statements, not because he thought he was funny but from sheer joy at life’s curious sweetness. That’s the impression I took, anyway, as his words came translated by Guangjian and his attitude shone merrily through. We climbed into his van and rode six miles to a village northeast of Lipu, where Mr. Wei turned onto a narrow lane, then through a gate, above which was a line of calligraphy announcing: SMALL HOUSE IN THE FIELD BAMBOO RAT RAISING FARM. Beyond was a courtyard surrounded on three sides by cinderblock buildings. Two wings of the building were filled with low concrete pens. The pens contained silver-gray creatures, small-eyed and blunt-headed, that looked like gigantic guinea pigs: Chinese bamboo rats. Mr. Wei gave us a tour up and down the rows.

  The pens were clean and well-drained, each furnished with a water dish and holding one to four animals. The Chinese bamboo rat is native to southern China and thereabouts, and the chewed-upon stalks of bamboo in some cages signaled that its diet is true to its name. The front teeth are beaverlike, well suited for gnawing those stalks, but in disposition a bamboo rat is more comparable to a pussycat. Mr. Wei lifted one by the scruff of its neck, turned it over, and gently poked at its sizable scrotum. Don’t try that with a beaver. The animal barely wriggled. Up and down the line we could see adults, juveniles, one female nursing two mouse-size pups, a mounting in progress. They breed readily, Mr. Wei explained. He kept mostly females, plus a few good studs. Last month he sold two hundred rats, and now he was expanding his operation, building new sheds. Already he was the largest bamboo-rat farmer in southern China! he told us exuberantly. Southern China, yes, and maybe beyond! After the expansions, with capacity for five thousand animals, he might be the largest bamboo-rat farmer in all China! He stated this not to brag, it seemed, but in joyous amazement at the vagaries of fortune. Business was good. Life was good. He laughed—ha ha ha!—at the thought of life’s goodness. He’s famous! he told us. He had been featured on Chinese TV! We could Google him! His ventures in bamboo-rat husbandry began in 2001, when he lost his job at a factory and decided to try something new.

  Enterprising and innovative, Mr. Wei now also had two pairs of large, rather menacing porcupines, which sulked in larger pens at the end of one room. He was diversifying. He had begun to breed them and, yes, their offspring too would be sold as food. A special product for special occasions, targeting the wealthier, more jaded epicure. A pair of porcupines was worth $1,000, Mr. Wei said. He did not lift one and poke its scrotum.

  I noticed several hypodermic syringes lying ready along the edge of a pen. Was he concerned about the health of his bamboo rats? I asked. Yes, very, said Mr. Wei, especially regarding viruses. They’re invisible. They’re dangerous. And you can’t run a bamboo-rat farm if the animals are sick. He showed us how he would inject an ailing rat on the inside of its calf. He didn’t mention what sort of medicine he injected, and most likely it was an antibiotic (therefore useless against viruses), not a newly developed SARS vaccine already available at the level of bamboo-rat wholesaling. But at least Mr. Wei’s animals might be free of common bacterial infections at time of sale. What they encountered thereafter—confined to their cages among tenements of other creatures, coughed upon, peed upon, shat upon by bats or civets or raccoon dogs in a warehouse or a wet market—that was a different matter.

  After the tour, Mr. Wei insisted we stay for dinner. He had commanded his family to prepare a small banquet. We sat at a low table on tiny chairs with an electric burner amid us, atop which Mr. Wei’s elderly mother assembled a formidable hotpot. Into the boiling broth she slid portions of chopped pork, chopped duck, some sort of potatolike tuber, enoki mushrooms, bean sprouts, bok choy, and greens from a plant related to morning glory. She stirred. She added dabs of salt. The ingredients cooked quickly, floated up, and combined to a savory stew, which we picked at with chopsticks and ladled into our rice bowls. Separately, on a cool platter, she offered us roasted gobbets of bamboo rat.

  The rat meat was mild, subtle, faintly sweet. There were many small femurs and ribs. One eats bamboo-rat hocks with one’s fingers, I learned, sucking clean the bones and piling them politely on the table beside one’s bowl, or else dropping them on the floor (the preferred method of Mr. Wei’s father, a shirtless old man seated to my left), where they would be scavenged by the skinny cat who slept under the table. The hotpot was scorching. Mr. Wei, an exemplary host, brought out some big bottles of Liquan beer, Guilin’s finest brew, nicely chilled. After a few glasses, I got into the spirit of the meal and found myself turning back to the rat platter, browsing for choice morsels.

  I had begun to see Aleksei’s point: If you’re a carnivore, you’re a carnivore, so what’s the merit of fine distinctions? And if you’re going to eat bamboo rat, I figured, best to do it here, at the source—before the poor animals get shipped, stacked amid other animals, and sick. Wild Flavor doesn’t need to be seasoned with virus.

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  Apart from the aftershock cases in early 2004, SARS hasn’t recurred . . . so far. The known events of the 2003 outbreak are still being interpreted. Many bits aren’t known. Many questions remain unanswered. Are bats the sole reservoir hosts of SARS-like coronavirus? If so, which kinds of bats? Is the coronavirus that was detected in least horseshoe bats the direct ancestor of SARS-CoV as found in humans? If so, how did the original spillover occur? Was it just a single transmission—from one bat into one civet—or several such happenings? And from civet into human—how many occurrences, how many independent spillovers? Did a cage full of infected civets, sold one by one in a market, send the disease off in multiple directions at once? What exactly happened on the ninth floor of the Metropole Hotel? Did Professor Liu vomit in the corridor, or did he merely sneeze, merely cough—merely exhale? How did the virus evolve during its passage through 8,098 humans? What role did the unique culinary culture of southern China play in bringing a dangerous pathogen out to Hong Kong and then to the world? Where do Mr. Wei’s bamboo rats go after leaving the Small House in the Field Bamboo Rat Raising Farm? How are they handled, amid what other animals, what piles of cages, what flying excretions, before reaching the restaurants of Guilin, Guangzhou, and Shenzhen? Why are some people superspreaders, when infected with this virus, but not others? What is the numerical value of R0 for SARS? When will the virus emerge again? Aleksei Chmura is just one researcher among many trying to add new data to the dossier in which these questions reside.

  Much has been written about SARS in the scientific literature since spring of 2003. Most of those papers are narrowly technical, addressing the details of molecular evolution, reservoir relationships, or epidemiology, but some ta
ke a broader view, asking What is it that makes this virus unusual? and What have we learned from the SARS experience? One thought that turns up in the latter sort is that “humankind has had a lucky escape.” The scenario could have been very much worse. SARS in 2003 was an outbreak, not a global pandemic. Eight thousand cases are relatively few, for such an explosive infection; 774 people died, not 7 million. Several factors contributed to limiting the scope and the impact of the outbreak, of which humanity’s good luck was only one. Another was the speed and excellence of the laboratory diagnostics—finding the virus and identifying it—performed by Malik Peiris, Guan Yi, their partners in Hong Kong, and their colleagues and competitors in the United States, China, and Europe. Still another was the brisk efficiency with which cases were isolated, contacts were traced, and quarantine measures were instituted in southern China (after some early confusion and denial), Hong Kong, Singapore, Hanoi, and Toronto; and the rigor of infection-control efforts within hospitals, such as those overseen by Brenda Ang at Tan Tock Seng. If the virus had arrived in a different sort of big city—more loosely governed, full of poor people, lacking first-rate medical institutions—it might have escaped containment and burned through a much larger segment of humanity.

  One further factor, possibly the most crucial, was inherent to the way SARS-CoV affects the human body: Symptoms tend to appear in a person before, rather than after, that person becomes highly infectious. The headache, the fever, and the chills—maybe even the cough—precede the major discharge of virus toward other people. Even among some of the superspreaders, in 2003, this seems to have been true. That order of events allowed many SARS cases to be recognized, hospitalized, and placed in isolation before they hit their peak of infectivity. The downside was that hospital staff took the first big blasts of secondary infection; the upside was that those blasts generally weren’t emitted by people still feeling healthy enough to ride a bus or a subway to work. This was an enormously consequential factor in the SARS episode—not just lucky but salvational. With influenza and many other diseases the order is reversed, high infectivity preceding symptoms by a matter of days. A perverse pattern: the danger, then the warning. That probably helped account for the scale of worldwide misery and death during the 1918–1919 influenza: high infectivity among cases before they experienced the most obvious and debilitating stages of illness. The bug traveled ahead of the sense of alarm. And that infamous global pandemic, remember, occurred in the era before globalization. Everything nowadays moves around the planet faster, including viruses. If SARS had conformed to the perverse pattern of presymptomatic infectivity, its 2003 emergence wouldn’t be a case history in good luck and effective outbreak response. It would be a much darker story.

  The much darker story remains to be told, probably not about this virus but about another. When the Next Big One comes, we can guess, it will likely conform to the same perverse pattern, high infectivity preceding notable symptoms. That will help it to move through cities and airports like an angel of death.

  Two days after our dinner at the rat farm, I rose early in Guilin, said my farewell to Aleksei Chmura, and caught a plane back to Guangzhou. I killed some hours in the airport there, paying more yuans for a ham sandwich and two lattes than I’d spent on a week’s meals in the cafés and noodle parlors of Guilin. Then I boarded my onward flight. In the row beside me were two young Japanese tourists, a couple, possibly returning from a romantic vacation amid the hotels, parks, malls, markets, restaurants, and crowded streets of Guangzhou or other cities of southern China. They took their seats unobtrusively and settled in for the short ride to Hong Kong. Maybe they felt a bit cowed by their own adventurousness and relieved to be headed home to a tidier nation; maybe they remembered the news stories about SARS. I didn’t intrude on them with questions. I wouldn’t have noticed them at all, except they were both wearing surgical masks.

  Yes, I thought, if only it were that simple.

  V

  THE DEER, THE PARROT,

  AND THE KID NEXT DOOR

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  Although the drumbeat has quickened in recent decades, the emergence of new zoonotic diseases isn’t unique to our era. Three stories exemplify that point.

  Q fever. Sixty years before Hendra, sixty years before Vic Rail’s horses started dying in that suburb of Brisbane, a very different sort of pathogen made its first recognized spillover in almost the same locale. It wasn’t a virus, though in some measure it behaved like one. It was a bacterium, but unlike most other bacteria. (An ordinary bacterium differs from a virus in several obvious ways: It’s a cellular organism, not a subcellular particle; it’s much larger than a virus; it reproduces by fission, not by invading a cell and commandeering the cell’s machinery of genetic copying; and it can usually be killed by antibiotics.) This new bug caused an illness that resembled influenza or maybe typhus. The earliest cases, occurring in 1933, were among abattoir workers in Brisbane, whose jobs involved slaughtering cattle and sheep. The affliction they suffered, known initially as “abattoir fever” among the doctors who treated them, acquired a more opaque name that stuck: Q fever. Never mind, for the moment, the origin of that name. The most notable thing about Q fever is that, even now in the age of antibiotics, for reasons related to its anomalous biology, it’s still capable of causing serious devilment.

  Psittacosis. Around the same time as Q fever emerged, in the 1930s, another peculiar bacterial zoonosis hit the news. This one also had links to Australia, but its scope was global, and it seems to have first reached the United States by way of a shipment of diseased parrots from South America. That was in late 1929, just in time for the Christmas season of parrot-giving. One unlucky recipient was Lillian Martin, of Annapolis, Maryland, whose husband bought her a parrot from a pet store in Baltimore. The bird keeled over dead on Christmas Day, a bad omen, and Mrs. Martin started feeling ill about five days later. Psittacosis is the medical name for the ailment she contracted; it passes from birds (especially those of the order Psittaciformes, meaning parrots and their kin) to humans, causing fever, aches, chills, pneumonia, and sometimes death. “Parrot fever” was the label under which it raised alarm in the United States during early 1930, when people exposed to those unhealthy imported birds started getting sick, especially in Maryland. PARROT FEVER HITS TRIO AT ANNAPOLIS was a typical headline, bruiting a story that ran in The Washington Post, on January 8, about Lillian Martin and two of her close relatives. Three days later, also in The Post: BALTIMORE WOMAN’S DEATH BLAMED ON PARROT DISEASE. Over the next several months psittacosis would become a national concern, causing enough reaction or overreaction that one commentator called the whole thing an example of “public hysteria,” commensurate with flagellation zeal and St. John’s fire in the Middle Ages.

  And then there’s Lyme disease. This seems to be a more recent version of the spooky-new-bacteria phenomenon. In the mid-1970s, two alert mothers in Lyme, Connecticut, near Long Island Sound, noticed that not only their children but a high incidence of other youngsters nearby had been diagnosed with juvenile rheumatoid arthritis. The odds were against any such concentration of cases occurring by chance. Once the Connecticut Department of Health and the Yale University School of Medicine had been alerted, researchers noticed that these arthritis diagnoses coincided with a particular pattern of skin rash—a red ring, spreading outward from a point—known to occur sometimes around tick bites. Ticks of the genus Ixodes, commonly called “deer ticks,” were abundant in the forests of eastern Connecticut and surrounding areas. In the early 1980s, a microbiologist named Willy Burgdorfer found a new bacterium in the guts of some Ixodes ticks, a likely suspect as the causative agent. It was a spirochete, a long spiral form, closely resembling other spirochetes of the genus Borrelia. After further research confirmed its role in the arthritis-like syndrome, that bacterium was named Borrelia burgdorferi in honor of its principal discoverer. Lyme disease is now the most common tick-borne disease in North America and one of the fastest-increasing infectious diseases of any so
rt, especially in New England, the mid-Atlantic states, and Wisconsin. Part of what makes it problematic is that the life history of Borrelia burgdorferi is very complex, involving much more than ticks and people.

  Lyme disease, psittacosis, Q fever: These three differ wildly in their particulars but share two traits in common. They are all zoonotic and they are all bacterial. They stand as reminders that not every bad, stubborn, new bug is a virus.

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  Parrot fever was recognized as far back as 1880, when a Swiss physician named Ritter described a household outbreak, of something resembling typhus, in which seven people got sick and three died. Because the illness showed certain pneumonia-like aspects, suggesting airborne transmission, Dr. Ritter called it “pneumotyphus,” but he was groping. Although he couldn’t identify what caused it, he did manage to pinpoint the site of common exposure: the house’s study. The only thing remarkable about that room was that it happened to contain a dozen caged birds, including finches and parrots.