Did Pangolin Trafficking Cause the Coronavirus Pandemic?

The elusive animals’ possible involvement in the origins of COVID-19 gives them a weird ambivalence: threatened and, perhaps, dangerous.

The town of Yokadouma lies in remote eastern Cameroon, close to the border with the Central African Republic, at a juncture of narrow roads that—when I visited, in May, 2010, near the end of the long dry season—were unpaved and parched, their laterite clay pounded to powder by logging trucks rumbling north from the Republic of the Congo. The town’s name translates as Standing Elephant, and in the central roundabout stood an elephant statue, its tusks and part of its trunk broken off, rebar protruding. I checked in to the Hotel Elephant, whose dining room had a gorilla skull hung on one wall, a python skin stretched beside it. I remember the place because it was here, on the following morning, that I met my first pangolin, which was also my last.

A young man from the kitchen staff had just brought this piteous creature back from the town market. He carried it by its tail as it dangled, groggy and helpless. It was reddish brown, like the roadside trees, and for the same reason—it was caked with dust. The scales covering its head, body, and tail looked like rusty metal feathers. Pangolins are amazing animals, loosely known as scaly anteaters because of their armored skin and their diet, their elongated heads and their toothless mouths, though they aren’t closely related to true anteaters. In fact, they constitute a group of their own, one of the oddest of mammalian orders, the Pholidota, which contains only eight living species (the order of bats comprises fourteen hundred species). They are similar to carnivores by descent, and to armadillos by convergent evolution. They eat termites as well as ants, but they are virtually incapable of harming any other form of living creature, except in their own defense.

The kitchen worker dipped this one into a storm sewer to revive it, then let it walk a few steps. Its snout was pointy, essentially an aiming device for its long, noodle-like tongue. Its eyes were dark little beads, shiny but uncomprehending. Its belly, unprotected by scales, was a pale-cream color. This was a white-bellied pangolin, one of four African species, three of which are native to southern Cameroon. It tried to hide, pushing its head into a small hole in the ground near the wall. But even with its sizable front claws, and the strength and instincts of a burrower, it had no chance of digging its way to safety. What will you do with it? I asked the young man. It would be eaten, he said. Pangolin is commonly consumed in Cameroon, as in many different parts of Central Africa and also in Asia, where the other four species are native.

They are elusive creatures, seldom seen even by those who spend considerable time walking in African forests. In 1999 and 2000, J. Michael Fay, an American ecologist and conservationist, made an epic foot journey, with the support of Congolese and Gabonese field crews: four hundred and fifty-six days through the last great intact forests of Central Africa, trekking a zigzag course from the northeast corner of the Republic of the Congo to the Atlantic Ocean, fording rivers, mucking across swamps, tunnelling by machete through trackless thickets, and sometimes strolling easily along elephant trails beneath closed forest canopy. Pausing every twenty paces or so, he recorded methodical notes and calibrations in his Rite in the Rain notebooks on every manner of biological observation. Through the length of his expedition, Fay saw one pangolin. I happened to be with him that day, but I missed it.

Yet pangolins are disastrously susceptible to capture by humans. When they are attacked or challenged, their default mode of defense is to roll into a ball, like a pill bug, scales on the outside, tender parts within. The name pangolin comes from peng-goling, which in Malay means “roller” or “that which rolls up.” This defense works well against such predators as lions and leopards but not against one with a brain and a pair of hands, capable of battering a pangolin open or carrying it back to a village.

Pangolins are also susceptible to coronaviruses, and that trait has given them an unexpected role in the mystery of how sars-CoV-2, the covid-19 virus, found its way into people. Sampling of tissues from dead pangolins has shown that some carry viruses very similar to sars-CoV-2. Did a population of these animals serve as intermediate hosts, within which a bat virus lived briefly—or maybe for some decades, acquiring adaptations that could make it devastating to humans? The evidence is complicated. And the question is only more charged given that all eight pangolin species are presently being pushed toward extinction. Their possible involvement in the covid-19 story gives them a weird ambivalence, endangered and (perhaps) dangerous. Even as so many humans suffer and die, it’s worth asking the pangolin question: has our hunger for these humble creatures got us into a global catastrophe?

Pangolins are solitary animals, each one foraging on its lonesome, the adults coming together briefly to breed. The female carries her single offspring piggyback for some months, and sleeps with it curled tenderly within her armor. Although pangolins are hard to find, they must have once seemed endlessly abundant. Between 1975 and 2000, according to the German biologist Sarah Heinrich and her colleagues, drawing on the database of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (a multinational compact known as cites), roughly seven hundred and seventy-six thousand pangolins became merchandise that was traded legally on the international market. That flow of products included almost six hundred and thirteen thousand pangolin skins, exported from countries including Malaysia, Indonesia, and Thailand.

Pangolin scales are a separate commodity, highly valued in some cultures for their supposed efficacy in traditional medicines. Between 1994 and 2000, almost nineteen tons of pangolin scales (accounting for roughly forty-seven thousand pangolins) were exported from Malaysia for use in traditional Chinese medicine (T.C.M.) in China and Hong Kong. Chinese tradition, as inscribed in old texts, holds that pangolin scales, ground to powder or burned to ash, can be useful against ant bites, midnight hysterias, evil spirits, malaria, hemorrhoids, and pinworm, and for stimulating lactation in women. Science doesn’t support these claims—the scales consist merely of keratin, the same material as your hair and your nails.

“There’s a lot of finger-pointing at other cultures,” Sarah Heinrich said recently from her home near Potsdam. The finger could point in many directions. Most of the pangolin skins exported between 1975 and 2000 went to North America, where they were turned into handbags, belts, wallets, and fancy cowboy boots. Pangolin leather was especially prized because the animal’s skin bears an eye-catching, almost reptilian, diamond-grid pattern. The Lucchese boot company, bootmaker to Lyndon Johnson, among others, produced pangolin-leather boots before 2000, when cites set the export quota for wild-caught Asian pangolins to zero, essentially making the international commerce illegal.

By then, the pangolin populations in China and parts of Southeast Asia had been drastically depleted, not just to make American cowboy boots but also for regional consumption. At one point, some hundred and fifty thousand pangolins in China went to the knife monthly, their meat eaten and their scales used in T.C.M. “Such was the magnitude of this exploitation,” the Oxford University-based pangolin expert Daniel Challender and three co-authors wrote, “that it apparently led to the commercial extinction of pangolins in China by the mid-nineteen-nineties.” Importing pangolins was more practical than hunting down the few indigenous ones that remained.

Challender did some of his doctoral field work in Vietnam, conducting market surveys, gathering price data on pangolin scales, visiting restaurants where the meat was served. “If you go into a restaurant in Ho Chi Minh City,” he told me, “you’re going to be paying three hundred and fifty dollars a kilo for a pangolin.” It might be grilled, or boiled in a hot pot with ginger and spring onions. He recalled sitting in a restaurant, in 2012, watching three diners enjoy a seven-hundred-dollar pangolin meal. A server carried the animal, alive, into the restaurant in an old sack. It was balled up in its defense posture, showing only scales and claws. “They took out a large rolling pin and clubbed it unconscious,” Challender said. Then “they took some scissors and used the scissor blades to cut the throat.” The blood was drained out and mixed with alcohol for the diners, and the flesh was cooked.

As the Asian populations declined, African pangolins began flowing east in large quantities. Since early times, many peoples of sub-Saharan Africa have “harvested” pangolins, trapping the animals with snares, tracking them with dogs, or coming across them in the forest. The hunters traditionally consumed their catch or sold it into local bush-meat markets. Eventually, the meat became popular in cities, too, such as Libreville, in Gabon, and Yaoundé, in Cameroon, and that led to rising prices around the start of the twenty-first century. The scales mostly moved through the ports and airports of Nigeria and Cameroon to Asia, especially China and Vietnam.

“I know we’re serving as a transit point,” Olajumoke Morenikeji told me recently. She’s a zoologist, and a founder of the Pangolin Conservation Guild Nigeria. To judge from the thousands of kilograms of scales seized, she said, “you can’t have all that just coming from Nigeria.”

Luc Evouna Embolo, an officer for traffic, an international network that monitors the wildlife trade, gave a similar account from Yaoundé. Increasingly, middlemen incite local people to collect pangolins from the field and sell to them. The middlemen sell to urban businessmen who illegally export the animals. A villager might get paid three thousand C.F.A. francs (roughly five dollars) for a pangolin that will be worth thirty dollars in Douala, Cameroon’s economic capital, and much more in China. In 2017, police made one seizure amounting to more than five tons of scales, for which two Chinese traffickers were arrested.

In late 2016, cites had decided to make all international trade of wild-caught pangolins and their parts illegal, but the traffic continued. Its scope could now be gauged only from the fraction seized by customs officials and other national enforcement authorities or detected by non-governmental investigators. By one estimate, almost nine hundred thousand pangolins have been smuggled during the past two decades. Some were alive. Some were dead, peeled of scales and frozen gray. The scales were concealed in sacks or boxes within shipping containers, sometimes labelled as cashews, oyster shells, or scrap plastic. Those who track this commerce, such as Challender and Heinrich, say that pangolins seem to be the most heavily trafficked wild mammals in the world.

There is a vogue in urban China for ye wei, or “wild tastes”—wildlife meat, supposedly imbued with healthful, invigorating properties. Some consumers cherish the notion that eating pangolin is a revered national tradition. But that notion has lately been challenged. Earlier this year, a Chinese journalist named Wufei Yu published an Op-Ed in the Times highlighting old texts that advise against consuming the flesh of certain wild animals, notably snakes, badgers, and pangolins. Yu found that in 652, during the Tang dynasty, an alchemist named Sun Simiao warned about “lurking ailments in our stomachs. Don’t eat the meat of pangolins, because it may trigger them and harm us.” A millennium later, in a compendium of medical and herbal lore now considered foundational to T.C.M., the physician Li Shizhen cautioned that eating pangolin could lead to diarrhea, fever, and convulsions. Pangolin scales could be useful for medicines, Li Shizhen allowed, but beware the meat.

Zhou Jinfeng, a noted conservationist who heads the China Biodiversity Conservation and Green Development Foundation, in Beijing, added a caustic dismissal. “It’s not a matter of tradition,” he told me by Skype. “It’s a matter of money.”

And now, along with the traffic of pangolins into China, a new concern has arisen: the traffic of certain viruses. There was an unheeded signal last year. On March 24, 2019, the Guangdong Wildlife Rescue Center, in Guangzhou, took custody of twenty-one live Sunda pangolins that had been seized by customs police. Most of the animals were in bad health, with skin eruptions and in respiratory distress; sixteen died. Necropsies showed a pattern of swollen lungs containing frothy fluid, and in some cases a swollen liver and spleen. A trio of scientists based at a Guangzhou governmental laboratory and at the Guangzhou Zoo, led by Jin-Ping Chen, took tissue samples from eleven of the animals and searched for genomic evidence of viruses. They found signs of Sendai virus, harmless to people but known for causing illness in rodents. They also found fragments of coronaviruses, a family high on the watch list of viruses potentially dangerous to humans. Still, this was not big news when the Chen group published its report, on October 24th. The scientists noted that either Sendai or a coronavirus might have killed these pangolins, that further study could help with pangolin conservation, and that such viruses might be capable of crossing into other mammals.

Three months later, the word “coronavirus” carried a different ring. An initial small cluster of “abnormal pneumonia” cases had appeared in Wuhan, the capital of Hubei Province; soon the number had exploded to thousands, and the city was in lockdown; Chinese sources had revealed that a “novel coronavirus” was the cause of this disease; the first genome had been sequenced and released, by a Chinese team led by Yong-Zhen Zhang, of Fudan University, and with one Western partner, Edward C. Holmes, who arranged to make the sequence public on a Web site called Virological, run by a colleague at the University of Edinburgh; cases had started turning up elsewhere, including South Korea, Singapore, and the United States; the World Health Organization had declared a global health emergency; and everyone was now watching. Scientists who understand zoonotic diseases—the diseases caused by pathogens that pass from nonhuman animals into humans—had begun asking, Which animal was the source? Everything comes from somewhere, and novel viruses come to people from wildlife, sometimes through an intermediary animal that may or may not be wild.

Bats were prime suspects, because the sars virus that surfaced in 2002—highly lethal and transmissible, but quickly contained by the middle of 2003—had been a coronavirus hosted by bats. The mers virus, which emerged on the Arabian Peninsula in 2012, even more lethal but less transmissible than sars-CoV (as that first virus became known), was also a coronavirus traceable to bats, though in that case the bat virus had established itself in camels for some decades before spilling over into humans. Another notion about the new virus’s host was snakes—a suggestion made in late January, 2020, based on tenuous evidence, and quickly dismissed.

The attention swung back to bats on February 3rd, when a group led by Zheng-Li Shi, of the Wuhan Institute of Virology, presented genomic data showing a close similarity between the new virus and a coronavirus sequence they had found, half a dozen years earlier, among horseshoe bats in a mine shaft in Yunnan Province, a thousand miles southwest of Wuhan. The genome of this bat virus, now called RaTG13, was 96.2 per cent identical to the new human coronavirus. This was strong evidence that the new virus originally came from bats, but a four-per-cent difference between the genomes was far from a perfect match. Four per cent, in fact, implies decades of evolutionary divergence. Where had the new virus spent that time—in what population of bats or other animals—and how had it spilled from one of them into its first human host? With those questions pending, another candidate for the intermediary emerged. On February 7th, the president of South China Agricultural University, in Guangzhou, declared at a press conference that a team from her institution, in work not yet published, had found what may be an intermediate host of the virus, bridging the gap between bats and humans: pangolins. According to a report by Xinhua, the official Chinese news agency, the pangolin virus that the researchers had investigated was a ninety-nine-per-cent match with the coronavirus showing up in people.

The announcement was an overstatement of what the researchers had found, but it caused a flurry of headlines. Even the cites secretariat, based in Geneva, echoed the claim, tweeting the next day that “#Pangolins may have spread #coronavirus to humans,” and sugaring that sour tweet with video footage of cute pangolins—one of them a female with a juvenile on her back—climbing tree branches and snooping for ants. The implication was: these adorable animals carry lethal viruses, so best to leave them alone. When the study from South China Ag. went online, the big result was not quite as big as advertised, though it was still dramatic. The coronavirus genome that these researchers had assembled, from pangolin lung-tissue samples, contained some gene regions that were ninety-nine per cent similar to equivalent parts of the sars-CoV-2 genome—but the over-all match wasn’t that close. Maybe two coronaviruses had merged in a single animal, the researchers wrote, and swapped sections of their genomes—a “recombination event.” Such an event may even have proved fateful, by patching one genomic section of a pangolin coronavirus together with a bat coronavirus. That section, known as the receptor binding domain (R.B.D.), endowed the composite virus with an extraordinary capacity to seize and infect certain human cells, including some in the respiratory tract.

The South China Ag. team got its samples from pangolins at the Guangdong rescue center, some of which had previously been sampled by Jin-Ping Chen’s group. The team’s study, of which Yongyi Shen was a senior author, gave vividness to a technical report when it noted that the rescued pangolins “gradually showed signs of respiratory disease, including shortness of breath, emaciation, lack of appetite, inactivity, and crying.” Pangolins are sensitive, hard to keep alive in captivity even under solicitous care; the harsh conditions of being trafficked internationally would make them especially susceptible to infection. But what killed those sixteen pangolins? Was it Sendai virus, or a coronavirus, or some other cause unrelated to concerns about human health? We’ll probably never know. Later in the paper, buried in a section on methodology, Shen and his co-authors added that the animals “were mostly inactive and sobbing, and eventually died in custody despite exhausting rescue efforts.” Sobbing might be taken as a metaphor for respiratory struggle, but, then again, sometimes a sob is just a sob.

On that morning in southeastern Cameroon, I left the doomed pangolin at the hotel—I knew I couldn’t save it except temporarily, and to salve my own conscience, by trying to buy it—and walked across Yokadouma to the local headquarters of the Ministry of Forests and Wildlife. In a conference room there, I met with the chief of the wildlife section, Apollinaire Otto Mbala, and several other officers, including Achille Mengamenya, the conservator of the nearby Boumba Bek National Park, who wore a military-style uniform with a thick belt and shoulder boards. We talked about legal hunting (for animals such as duikers, small forest antelopes), illegal hunting (for gorillas and chimpanzees), and the status of elephants (they could sometimes, in some areas, be fair game). When bush meat was confiscated, Mbala told me, it was auctioned, the proceeds going into ministry coffers. We also discussed aids, a severe problem in the region and my reason for coming to southeastern Cameroon: to investigate the connection between wildlife as food and the emergence of that disease.

Humans are especially susceptible to viruses from our closest evolutionary kin, and I was interested in the passage of a certain chimpanzee virus into its first human host. Back at the Hotel Elephant, I had a journal paper, much annotated during my rereadings, by a group led by Beatrice H. Hahn, then of the University of Alabama at Birmingham, that cast light on the geographic origin of the aids pandemic. Hahn and her colleagues pioneered a technique of extracting viral genomic evidence from chimpanzee fecal samples and, by comparing those data with H.I.V. genomes, had located the chimpanzee population from which a simian virus (now called sivcpz) spilled from a single chimp into a single human, with catastrophic results for tens of millions of people. The spillover evidently occurred in the extreme southeastern corner of Cameroon. Many chimps across Africa are infected with variants of the sivcpz virus. But those in southeastern Cameroon carry what seems to have become the exact pandemic strain of the aids virus. How had the spillover happened? Possibly during an act of butchery, after the human had snared or speared the chimp; at that point, a cut on the human’s hand or arm could have allowed blood-to-blood transfer of the virus. This scenario was speculative, and it came to be known as the cut-hunter hypothesis.

Mbala turned his laptop to show me a photo of a dead gorilla, killed six months earlier, not far from the national park. The poacher had escaped. What happened to the gorilla’s body? I asked. Mbala hesitated uncomfortably, then said that it had been auctioned: “The locals will eat it. It is meat, after all. It’s very valuable.”

Chimpanzees are valued similarly. From an officer of a conservation group in Yokadouma, I heard about a circumcision ceremony called beka, practiced by the Bakwele people of the region, for initiating a young boy into manhood. He said that it involves an all-night vigil, continuous drumming, certain drugs to keep the boy awake, a bath at dawn, then a day of walking, and finally the crescendo, when a masked officiant cuts off the boy’s foreskin. Traditionally, beka also required the amputated arms of a chimpanzee, to be eaten by village elders. Recently, the Bakwele had shifted to gorilla arms, the officer told me, because of availability. “Chimps are becoming more and more scarce.”

Two days later, I accompanied Mengamenya, the conservator, on an anti-poaching sweep through Boumba Bek National Park. We crossed the Boumba River by dugout canoe, bushwhacked through the forest, counted gorilla nests, waded along waist-deep channels, followed muddy trails potholed with elephant footprints, and looked for signs of people who shouldn’t be there. We found an abandoned poachers’ camp, with three thatched-roof shelters, a fish-drying rack (beneath which a fire still smoldered), and a small bag of reya chips, a traditional poison made from the seeds of a vine. At the tip of an arrow, it would work against monkeys and other small game, Mengamenya explained, and he ordered the camp burned.

We slept on the riverbank and continued the next day. As we walked, Mengamenya answered my questions about traditional hunting in this part of Cameroon. The reya poison, for instance: a hunter would grind it to powder, apply it to crossbow arrows, shoot a monkey, then follow the animal for half an hour until it fell, helpless, out of a tree. Hunting gorillas required dogs, many men, and a chaotic process of surrounding a big ape and then spearing it. (Hunting with rifles or shotguns was easier, of course, but many local people couldn’t afford them, and we had seen no spent ammunition.) Chimpanzees were generally taken with snares, and the dangerous moment was when a hunter closed in on that tethered, frantic, enraged animal to finish it with a spear. “Il y en avait beaucoup d’accidents de chasse,” Mengamenya said. Lots of hunters got hurt. Chimpanzees are powerful, and they bite. It reminded me of the hypothetical cut hunter. A moment of bloody contact could yield many bad outcomes, one of which was infection with a new virus.

This answered the question that had brought me to southeastern Cameroon: Yes, the hunting and eating of chimps and gorillas continues. And, as long as it does, humanity stands in jeopardy of another spillover the likes of H.I.V. But, of course, subsequent events have shown, too, that apes aren’t the only animals hosting viruses to which humans may be catastrophically susceptible.

Stories, in our connected era, spread even more quickly than viruses. One story of covid-19 that spread early and widely was that the outbreak had begun among people associated with the Huanan Seafood Wholesale Market, in Wuhan. It was a wet market, where venders offered wildlife for eating—from civets to wolf pups, porcupines, and snakes—as well as seafood, domestic meat, and other perishable food items. (Pangolins would have been traded less openly.) The market was shut down on January 1st, in response to the “abnormal pneumonia” outbreak, and scientists took samples in search of what they may have suspected—but no one had yet declared publicly—was a novel coronavirus. Then the market was promptly cleaned by a team of masked, white-clad workers spraying sanitizer. The coronavirus was found—genomic bits, plus a touch of viable virus that could be grown in a lab—but it came from wastewater or door handles or other surfaces, not from wild animals. If any live animals caged at Huanan were tested for the coronavirus, those results have never been announced.

A later review of the first forty-one hospitalized patients clarified that most, but not all, of them had been exposed to the market. Some—including the earliest patient, whose symptoms began on December 1, 2019—had no known contact with Huanan. This suggests that the coronavirus was already circulating among people in the city as early as November, and that an infected person—not an infected wild animal—may have carried it into the market.

The first human victim probably did get infected from a wild animal. But it’s unknown whether that animal was a bat or a pangolin or something else, or whether it was in a cage on its way to Wuhan, or maybe living in the wild, defecating on somebody’s vegetable garden.

As the pandemic took hold, the Chinese government enacted several measures against the sort of commerce that made wet markets notorious. On February 24th, the Standing Committee of the National People’s Congress, China’s highest legislative body, adopted a ban on selling or eating wild animals. On June 5th, pangolins native to China were upgraded to the highest level of wildlife protection. Days later, word leaked that pangolin scales would be removed from the “Chinese Pharmacopoeia,” the official compendium of T.C.M.

Uncertainty over the origins of the virus continued. At least three more scientific papers on the subject appeared between February and May, two from Chinese teams and one from a group at the Baylor College of Medicine, in Houston. All three based their analyses, as had Yongyi Shen’s group at South China Ag., on genomic data from pangolins at the rescue center in Guangdong. One group reported that pangolins seem to carry a coronavirus so similar to sars-CoV-2 that it might be the source of the pandemic. Part of their evidence was that crucial section of the pangolin coronavirus genome, the receptor binding domain, which bears an uncanny resemblance to the R.B.D. in the pandemic virus. Another group said, No, our analyses do not support the idea that the pandemic virus came directly from a pangolin. The third group, posting their report as a preprint, before peer review, agreed with Yongyi Shen: this sars virus looks as though it could be the result of a recombination event—a switching of genome segments in the body of one animal—or maybe several such events, accidentally combining genes from bat viruses, pangolin viruses, and even other viruses to become the extremely well-adapted virus causing the nightmare of covid-19.

There’s also a possibility that the viruses carried by smuggled pangolins do not reflect the typical viral burden of wild pangolins. They might not really be pangolin viruses at all, but infections acquired from other wild animals under the conditions of the trafficking chain—stress caused by shortage of food and water and oxygen, human handling, temperatures too hot or too cold, close confinement in cages adjacent to various doomed creatures. That could explain the respiratory symptoms: pangolins, unlike bats, may be unaccustomed to these viruses. One group of scientists looked at pangolins near the supply end of the trade flowing toward China, collecting throat and rectal swabs from three hundred and thirty-four Sunda pangolins in Peninsular Malaysia and the state of Sabah (Malaysian Borneo) that had either been seized from smugglers, or otherwise rescued, between 2009 and 2019. Not one sample tested positive for a coronavirus.

The scientific discussion of the pandemic’s origins is still in kaleidoscopic flux. Among even just the hypotheses for which empirical evidence exists—ignoring the nutcase theories, the unsupported slanders, and the paranoid speculations purveyed online—ideas vary, and some sets of data conflict with others. Journal papers are appearing faster than ever, many of them posted, before peer review, on such “preprint” Web sites as bioRxiv, hosted by the well-respected Cold Spring Harbor Laboratory, on Long Island. Others get peer-reviewed quickly, because of their urgency, and go online under the aegis of eminent journals including Nature, Cell, and The Lancet. Still another paper, published this spring by Nature, examined samples from a different batch of rescued pangolins—from Guangxi Province—as well as genomic evidence from the much studied Guangdong pangolins. These scientists found two distinct lineages of coronavirus closely related to sars-CoV-2.

Two coronaviruses, both resembling our nemesis bug? It seemed to suggest that pangolins are brimming with invisible menace. The first author on the Nature paper was Tommy Tsan-Yuk Lam; the senior author was a famed virus hunter in Hong Kong, Yi Guan; and among the other authors was Edward C. Holmes, who brokered the release of the first sars-CoV-2 genome. So I asked Holmes, by Skype, for illumination.

Edward C. Holmes is a brilliant evolutionary biologist, the author of an authoritative book, from 2009, titled “The Evolution and Emergence of RNA Viruses” (they are the fastest-evolving and most dangerous kinds of virus, and include the coronaviruses). Born in England, Holmes is now a professor at the University of Sydney, with close connections to colleagues in China. He has a quick wit and a perfectly round, bald head. His friends and his Twitter followers know him as Eddie. When I first met him, ten years ago, at Penn State, where he worked at the time, his office was decorated with a poster depicting Bart Simpson in a cartoon version of “Nighthawks,” the Edward Hopper painting. Why Bart Simpson? I asked. Because he looks like me, Holmes said.

“In February, I get contacted by Tommy Lam,” he told me now. Lam, a former postdoctoral fellow of Holmes’s, was working in Hong Kong with Yi Guan. Lam explained that he and Guan had obtained viral genome sequences from pangolins confiscated by customs authorities in two different provinces—not just the rescue-center ones but also some seized during 2017 and 2018 in Guangxi Province, which shares a border with Vietnam and therefore lies along a pangolin-trafficking route. Two things were notable about the animals, Lam told Holmes: “They’ve got this respiratory disease. And guess what. They’ve got, like, this coronavirus in them.” Another coronavirus, not a familiar one, but also resembling sars-CoV-2. Holmes told me, “I thought, Well, that’s extraordinary.”

Holmes signed on to assist with his specialty, analyzing genomic data. What surprised him was not just that two distinct groups of pangolins both carried coronavirus infections, or that both viruses were similar to the human virus, but that they were distinct from each other. “That’s what is so striking,” he said. “There are two lineages, and the Guangdong ones are closer to sars-CoV-2 than the Guangxi ones. But they’re both close. Right? So it’s not that there’s one outbreak in pangolins.” Two distinct coronaviruses, each similar to sars-CoV-2, one with a receptor binding domain to which human-lung cells are highly susceptible, had travelled into southern China in smuggled pangolins.

“What are the odds?” Holmes said. The odds are low. The finding suggests, he added, that there are many more dangerous viruses lurking in pangolins than we have detected so far. But not just in pangolins—don’t forget bats, carrying their own share of coronaviruses, some of which are only a few decades of evolutionary change from having the capacity to infect and kill humans. And not just bats. What other animals may have played a role during that stretch of missing decades, which he called the evolutionary gap? “What’s in the gap?” he asked. “I don’t know. Raccoon dogs?” Raccoon dogs are tree-climbing canids with black masks, native to East Asia and also sold as food. “Bamboo rats?” Confession: I’ve eaten those, in China, myself. “Who the hell knows?” Holmes said. “But until we go there and sample them we’re never going to know. That’s the critical thing. To resolve the origins.”

More field research is needed, he meant. More sampling of wild animals. More scrutiny of genomes. More cognizance of the fact that animal infections can become human infections, because humans are animals. We live in a world of viruses, and we have scarcely begun to understand this one. 

David Quammen is the author of many books, including “The Song of the Dodo,” “Spillover,” and, most recently, “The Tangled Tree.”