Exclusive: Inside the Thriving Wild-Animal Markets That Could Start the Next Pandemic

Live-animal markets are a natural laboratory for viruses to evolve and spark deadly outbreaks, yet scientists lack support to study the risks they pose.

In the bustling Jatinegara market in Jakarta, cages are stacked three metres high, holding creatures from all corners of Indonesia and beyond. Bats, raccoon dogs, macaques and songbirds — sold as pets or food — are crammed together, their musky odours mingling with the stench of urine and faeces in the damp tropical air.

For decades, public-health experts have warned about the risks of infectious diseases jumping from animals to humans in markets such as Jatinegara, which are part of a global industry worth hundreds of billions of dollars annually. These markets remain “the best way of transmitting diseases,” says James Wood, a veterinary epidemiologist at the University of Cambridge, UK. Jatinegara’s location, in an international travel hub with a population of 11 million people, increases that risk considerably.

The world is still recovering from the COVID-19 pandemic, which many researchers say probably started, or was at least amplified, at a market selling live animals in Wuhan, China^1,2. Yet the wildlife trade still thrives in many parts of the globe. China banned the farming and trading of most wildlife species for food in 2020, but these practices have simply gone underground. “We are back to business as usual,” says Vincent Nijman, a conservation biologist at Oxford Brookes University, UK, with “millions and millions of animals being traded on a daily basis.”

The wildlife trade acts as a vast global network of unregulated natural laboratories, through which potential pathogens freely circulate, evolve and ultimately congregate in urban centres, says Andrew Cunningham, a wildlife epidemiologist at the Institute of Zoology in London. “It’s the scariest thing we are doing,” he says.

Before the pandemic, there was a strong emphasis on identifying new viruses in the wild. These efforts were driven by the idea that it might be possible to predict which viruses could spark major disease outbreaks. But many researchers now say that this assumption was flawed.

Increasingly, scientists are looking to human — wildlife interfaces — including markets and the trade networks that supply them — as crucial sites for the study of zoonoses, human diseases caused by pathogens that normally infect other species. A handful of research groups are now working to understand how pathogens jump between species, why some jumps cause outbreaks and others don’t, and what kinds of intervention can reduce the risks. But such work is costly, can be dangerous and demands sustained support, which has become increasingly hard to secure.

Without investing in such research, “you’re really flying blind,” says Maria Van Kerkhove, head of the emerging diseases and zoonoses unit at the World Health Organization in Geneva, Switzerland. “You’re making recommendations that may not be the most appropriate.”

Poster child

In the veterinary room of Cuc Phuong National Park in Vietnam, Tran Nam Trieu carefully lifts a Sunda pangolin (Manis javanica) onto an examination table. The creature is curled into a ball, its scales subtly rising and falling with each breath. Confiscated near the border with China in early 2023, it is now in the care of Save Vietnam’s Wildlife, a non-profit conservation organization that runs a rescue centre at the park. Delicately unrolling it, Trieu, a veterinary surgeon, reveals its soft pink belly and the wound from an amputation; its left hind leg was damaged in a snare.

The enormous demand in China for pangolin meat and scales — believed, without evidence, to cure a wide range of ailments — has made these creatures the poster child of the illegal wildlife trade. And studies of confiscated pangolins in China have detected several types of coronavirus that share up to 92% of their genome with SARS-CoV-2, the virus that causes COVID-19³. Although too distantly related to have given rise to SARS-CoV-2, the viruses sometimes cause COVID-19-like symptoms in these animals and might have the potential to infect humans.

Other coronaviruses found in these pangolins are relatives of those that cause Middle East respiratory syndrome (MERS). The virus spike proteins have a feature known as a furin cleavage site⁴, thought to be crucial for the viruses to replicate efficiently in the respiratory tract. The presence of a similar feature in SARS-CoV-2 has contributed to the suspicion that the virus might have been engineered by researchers at the Wuhan Institute of Virology — although it could also have arisen naturally.

Wood recognizes the “small possibility” that research-associated activities could have triggered the pandemic. But that “should not prevent us from focusing on the bigger picture,” he says: the wildlife trade poses a much greater zoonotic risk than do lab accidents.

To gauge those risks, Nguyen Thi Thanh Nga, a researcher at the Wildlife Conservation Society (WCS) in Hanoi, and her colleagues are working to identify potential pathogens circulating in trafficked pangolins in Vietnam — a major transit hub for moving wildlife into China — and exploring how these microorganisms relate to those found in source and destination countries. Of 246 pangolins confiscated across Vietnam between 2015 and 2018 — many from the rescue centre in Cuc Phuong — 7 were infected with coronaviruses, although none had signs of respiratory or other systemic illnesses⁵. Partial sequences of these viruses closely resemble those of viruses found in pangolins seized in China.

Pangolins further upstream in the supply chain, however, seemed unaffected: none of the 334 pangolins confiscated from smugglers or rescued from the wild in Malaysia between 2009 and 2019 tested positive for coronaviruses⁶.

The increasing detection rate of coronaviruses along the supply chain is consistent with another study by WCS researchers, on rats captured and sold for food in Vietnam⁷. The team found that the proportion of rats that tested positive for coronaviruses was tenfold higher at the markets and restaurants where they’re sold than in the fields where they’re caught.

Trade routes

Some researchers are working to get a better handle on the human behaviours that help zoonotic viruses to thrive and spread. In 2017, Jusuf Kalengkongan, a behavioural scientist and founder of the Sulawesi Bat Conservation organization in Airmadidi, Indonesia, spent months living among wildlife hunters in villages in the province of Southeast Sulawesi. Capturing and handling bats can be dangerous work, he says, and some hunters develop fevers when wounds from a scratch or bite become infected. Rather than seeking hospital care, they typically take herbs and over-the-counter medications, he says. Village elders recalled a mysterious disease outbreak in which dozens of people died in a few weeks, Kalengkongan says.

Hung Nguyen-Viet, an animal-health specialist at the International Livestock Research Institute in Nairobi, Kenya, is leading a similar project in Vietnam. Researching trade networks, he says, is sensitive work that requires significant trust-building. A key question his team seeks to answer is: what do people do when the wild animals they capture fall ill? Some people choose to eat them, whereas others try to sell them to unsuspecting customers at a market far away, says Nguyen-Viet. Few, he says, would report it to the authorities, for fear of consequences to their livelihoods.

Medical anthropologist Hannah Brown at the University of Durham, UK, says that attempts to regulate the wildlife trade need to take these fears seriously, or risk pushing the activity further underground. This happened when the consumption of wild-animal meat was banned in West Africa during the 2014–16 Ebola epidemic, which was suspected — but never proved — to have been caused by the eating of bats. Ten years on, says Brown, people there are still negatively affected by the policy and remain suspicious of the authorities and international researchers.

Some scientists have managed to cultivate the trust of wildlife traders in Indonesia. At the Langowan market in North Sulawesi, which sells both wild-animal meat and live animals, Tiltje Ransaleleh asks vendors about their supplies, the species they’ve sold and their origins. Beneath a canopy of red fabric that wards off the tropical Sun, Ransaleleh, a zoologist at Sam Ratulangi University in Manado, Indonesia, and her colleagues collect swab samples from bats lining the wooden stalls.

Her team has mapped an intricate network of supply chains and identified the intermediaries — who purchase wild animals (including up to one million bats a year) from hunters and transport them to markets — as a potential vehicle for disease transmission⁸. One insight gleaned, she says, is that festive periods are the riskiest, when sales can surge to 5 times their usual volume, with more than 10,000 bats sold in a single day at Langowan.

Sea change

These in-depth studies of trade networks and human behaviour are essential for tracking the movement of wild animals and the potential pathogens they carry, says Stephen Luby, a disease ecologist at Stanford University in California.

In Côte d’Ivoire, for example, a team led by Fabian Leendertz, director of the Helmholtz Institute for One Health in Greifswald, Germany, is working to trace the movement of microbes from the Taï forest to village markets by systematically collecting samples from wildlife, humans and the environment they share. Later this year — partly supported by a €20-million (US$23-million) European programme called ZOOSURSY — the team will begin analysing samples from people with undiagnosed illnesses to explore potential links to wildlife exposure.

Technological breakthroughs could help researchers to analyse the samples from such projects without having to work with live viruses, says Christian Happi, director of the Institute of Genomics and Global Health in Ede, Nigeria. In collaboration with the Broad Institute of MIT and Harvard in Cambridge, Massachusetts, his team is developing a system that uses CRISPR gene-editing technology to simultaneously detect dozens of pathogens — such as the viruses that cause Ebola, mpox and West Nile disease. Previously, scientists could test for pathogens only one at a time. The system can be used in conjunction with ‘metagenomic’ studies that aim to sequence all the genetic materials in a biological sample, says Eddie Holmes, a virologist at the University of Sydney in Australia. The resulting sequences can be compared with known microbial sequences to identify new potential pathogens. Scientists can infer cross-species transmission by constructing genetic family trees that reveal the evolutionary relationships between microbes.

Meanwhile, a technique called VirScan allows scientists to screen for current and past infections in animals and humans by searching for antibodies to hundreds of microbial protein fragments, or epitopes, in a single test. It’s essentially “extreme serology,” says Linfa Wang, who studies emerging diseases at the Duke–NUS Medical School in Singapore. His team is using VirScan to map patterns of wildlife exposure in southeast Asian communities. A preliminary analysis revealed previously unrecognized epitopes, potentially leading to the identification of new viruses, says Wang.

Political headwinds

Although many questions about disease emergence remain unanswered, there are interventions that can make the wildlife trade safer without jeopardizing the livelihood of local communities, says wildlife veterinary surgeon Richard Kock at the Royal Veterinary College in London. For instance, the trade in animals known to pose high zoonotic risks — such as civets and raccoon dogs — could be restricted. Moreover, he says, national and international regulatory bodies could apply the same biosafety standards to trading wildlife as they do for livestock. This includes making markets a lot more hygienic, improving drainage and ventilation systems and providing personal protective equipment to those who handle wild animals.

The pandemic has, however, left a legacy that undermines global efforts to prevent future outbreaks. Zoonotic diseases, often associated with blame, stigma and punitive measures, have become a sensitive subject in many parts of the world and increasingly difficult to study. Individuals involved in the wildlife trade — from traders and market managers to regulators — are reluctant to participate in research. “They don’t want to know what might be there,” says Holmes, who unsuccessfully sought permission to collect samples from wild animals confiscated by Australian customs officials. “If you find something new, it becomes a problem,” he says.

Scientists in several southeast Asian countries told Nature that they’ve withheld information about newly identified pathogens because government officials didn’t authorize publication. “It’s a growing problem,” Van Kerkhove says. “The big thing for me that occupies a lot of my time thinking about is around incentives and disincentives.” What are the incentives for better regulation? What hinders effective monitoring? What could motivate the timely release of information when the only outcomes seem to be stigma, trade restrictions and travel bans?

Meanwhile, political support for tracking emerging diseases has fallen drastically since the brief surge immediately after COVID-19 emerged. The lack of clarity about the pandemic’s origins led to heightened anxiety over lab biosafety and an intense distrust of scientists researching emerging pathogens, Luby says. This is particularly pronounced in the United States, resulting in a general reluctance to fund such work. In 2023, it even led to the termination of a $125-million programme called DEEP VZN, funded by the US Agency for International Development (USAID) to improve the understanding of zoonotic disease in low- and middle-income countries.

Now, US President Donald Trump has ceased almost all USAID functions and funding, including the $100-million STOP Spillover programme, which aimed to develop interventions to mitigate zoonotic risks. The United States has decided to withdraw from the World Health Organization and has restricted federal funding for foreign research partners. Al Ozonoff, a scientist at the Broad Institute who collaborates with teams in West Africa on disease monitoring, says that several of his projects in Africa have lost funding. “It has been unsettling, discouraging and stressful,” he says.

These actions have created a void in the global disease-monitoring landscape that no other nation or organization is likely to fill, researchers say. “It’s not just a hole,” says Julien Cappalle, a disease ecologist at the French Agricultural Research Centre for International Development in Montpellier, who leads several European projects on emerging diseases. “Half the sky has fallen,” he says. What stands to be lost is not only the continuity of data collection, but also crucial efforts to build local capacity for timely detection of and response to disease emergence — as well as the trust and solidarity that are essential to these efforts, he says.

As for what will happen next, Cappalle adds, “we can only anticipate a decrease in this funding, until the next major crisis.”