Wildlife Trade Fuels Cross-Species Disease Transmission

A new study published in the journal Science has quantified the link between the global wildlife trade and the transmission of pathogens to humans, finding that the trade significantly accelerates the spillover of infectious diseases.

The research indicates that more than 40% of mammal species traded for traditional medicines, fur, food, and research carry at least one pathogen that causes disease in humans. By comparison, only 6% of non-traded mammal species share such pathogens.

This data shows that traded mammals are 1.5 times more likely to harbor human-infecting pathogens than species that are not traded.

The Impact of Trade Duration and Market Conditions

The risk of pathogen transmission increases based on how long a species has been circulated within trade networks. The study found that for every 10 years an animal species spends in the wildlife trade, it shares an average of one new pathogen with humans.

Certain environments within the trade present higher risks. Species sold in live-animal markets share an average of 1.5 times more pathogens with humans than other traded mammals.

These risks are intensified in live animal markets and the illegal wildlife trade, where animals from different species and regions are packed together under unsanitary and stressful conditions, creating more opportunities for viruses, bacteria, and other pathogens to jump into human populations.

Research Methodology and Data Sources

The study, led by Jérôme Gippet, an ecologist at the University of Fribourg in Switzerland, is the first to provide global quantitative evidence of the link between wildlife trade and pathogen transmission.

Researchers analyzed 40 years of global wildlife trade records from three main data sets. The team focused specifically on mammals because they are abundant in the trade—with approximately one-quarter of all mammal species being traded—and have a documented history of transmitting pathogens to humans.

The analysis relied on the VIRION database, an open atlas of more than 9,000 vertebrate viruses. This database is managed by the Viral Emergence Research Initiative (Verena), a multi-institutional research program at Yale University supported by a National Science Foundation grant.

Wildlife trade has been affecting our health much faster and for much longer than we thought, said Dr. Colin Carlson, an assistant professor of epidemiology at the Yale School of Public Health and co-author of the study.

Public Health Context

The findings provide a quantitative framework for understanding how the wildlife trade contributes to global health threats. Several major human disease outbreaks have already been linked to traded wildlife, including the emergence of HIV, the COVID-19 pandemic, and the 2014 West African Ebola epidemic.

By identifying the correlation between the duration of trade and the number of shared pathogens, the research suggests that the continued circulation of wild animals in trade networks increases the likelihood of future disease outbreaks.