A study conducted at the Department of Ecology and Evolution of the University of Lausanne (Unil) quantifies the impact of wildlife trade on the exchange of germs and parasites between animals and humans. It was published on 9 April 2026 in the journal Science.
Hedgehogs, elephants, pangolins, bears or fennec foxes: many wild species are sold as pets, hunting trophies, for traditional medicine, biomedical research, or for their meat or fur. These practices, whether legal or illegal, concern one quarter of all mammal species.
The team led by Cleo Bertelsmeier , Associate Professor at the Department of Ecology and Evolution (DEE) of the Faculty of Biology and Medicine at Unil, assessed the role of international wildlife trade in the transmission of pathogens between animals and humans. While this link has seemed obvious since Covid-19 – reminding that the sale of animals at the Wuhan market was singled out – "no precise quantification had been carried out until now," explains Jérôme Gippet , first author of the study published on 9 April 2026 in Science.
Forty years of trade data analysed
The team combined forty years of legal and illegal wildlife import-export data with compilations of host–pathogen relationships. Their analyses, conducted in collaboration with U.S. researchers (Yale University, University of Maryland and University of Idaho), led to the following result: wild mammals that are traded are 1.5 times more likely to share infectious agents with humans than those that are not involved in trade. "In other words, these species have a 50% higher probability of sharing at least one virus, bacterium, fungus or parasite with us." And that is not all: the risk is even higher when species are traded illegally or alive (for example as exotic pets).
The most striking finding according to the research team is that "the length of time an animal has been present in trade plays a key role: on average, a species shares one additional pathogen with humans for every ten-year period spent on the market," emphasizes Jérôme Gippet, former postdoctoral researcher at the DEE, now at the University of Fribourg.
Wildlife in all its forms
The work focuses on wild mammals, meaning species that have not been domesticated and on which humans have therefore not exerted selective pressure, unlike cats, dogs, cattle or camels. These may be individuals captured from the wild or bred in captivity, for example for fur production. This category also includes new exotic pets – fennec foxes, otters, African pygmy hedgehogs, leopard cats or sugar gliders, to name but a few – whose buying and selling are fuelled by their popularity on social media. The data analysed cover both the trade in live specimens and in animal-derived products (fur, skins, scales, horns, etc.).
"It is important to understand that the probability of being infected by playing a piano with ivory keys or wearing fur is almost nonexistent. The problem lies at the beginning of the chain: someone had to hunt the animal, skin it, transport it…," explains Jérôme Gippet. "Thus, even if the danger is not immediate, our consumption choices indirectly fuel the transmission of pathogens to humans. This calls our purchasing practices into question," adds Cleo Bertelsmeier, who led the study.
At the intersection of ecology and public health
The team led by Cleo Bertelsmeier initially became interested in wildlife trade because it is a source of biological invasions ( see related news in French ). Individuals can escape or be released into the wild and cause harm to local ecosystems. But this activity can also have two other consequences: first, the risk of species extinction due to overexploitation of natural populations; second, the risk of pathogen exchange with humans, which is the focus of this latest Science publication, a phenomenon that can lead to epidemics or even pandemics. Covid-19 is only one example among others: in 2003, the United States notably faced an outbreak of monkeypox transmitted by prairie dogs sold as pets.
Strengthening biosurveillance
The results of the study highlight the need to improve biosurveillance of animals and animal-derived products in order to detect infectious agents and assess their potential for transmission to humans. Currently, the main multilateral agreement governing international trade in wild species, CITES, focuses exclusively on preventing extinction.
"Our finding that wild mammals share, on average, one additional pathogen with humans for every decade of presence on the global market highlights that the number of contacts plays a decisive role. To reduce disease emergence, these opportunities for encounters must be limited, and therefore the overall volume of trade," states Jérôme Gippet.
"In my view, our work clearly shows how fundamental research can shed light on public health issues. It provides key elements to better understand host–pathogen dynamics and prevent future epidemics," concludes Cleo Bertelsmeier.
