Animals traded through global wildlife markets are far more likely to carry diseases that can infect humans, and the risk grows the longer those species remain in circulation, according to a new study.<\/p>\n
The analysis, published Thursday in Science<\/a>, examined decades of global wildlife trade data and found that 41% of traded mammal species share at least one pathogen with humans, compared with just 6.4% of species not involved in trade.<\/p>\n The researchers also found that the number of pathogens shared between animals and humans increases over time. On average, a species acquires one additional human-infecting pathogen for every decade it is present in the global wildlife trade.<\/p>\n The findings suggest that wildlife trade does not simply expose humans to existing disease risks, but may actively amplify them over time.<\/p>\n \u201cOur study is the strongest evidence to date that reducing wildlife trade will reduce pandemic risk,\u201d said Colin Carlson, an epidemiologist at the Yale School of Public Health and a co-author of the study.<\/p>\n Scientists have already long linked wildlife trade to specific outbreaks such as HIV<\/a>, Ebola<\/a> and COVID-19<\/a>. The new research, which draws on 40 years of global trade records and pathogen data, attempts to measure the relationship on a larger scale.<\/p>\n The results point to a broader pattern. Repeated and prolonged contact between humans and wild animals creates more opportunities for pathogens to move between species.<\/p>\n \u201cWhat stands out most is how clearly the findings reinforce something many of us in disease ecology have been concerned about for years: it\u2019s not just the presence of wildlife trade, but the intensity and duration of contact that elevates risk,\u201d said Thomas Gillespie, a professor of environmental sciences and environmental health at Emory University, who was not involved in the study.<\/p>\n Wildlife trade, as defined in this study, includes a wide range of activities, from hunting and breeding to transport, storage and sale. At each stage, animals are handled, confined and often brought into close proximity with both humans and other animal species. These conditions can facilitate the spread of viruses, bacteria and parasites.<\/p>\n Over time, those repeated interactions create more opportunities for pathogens to circulate, adapt and potentially spill over into human populations.<\/p>\n Carlson said one of the most striking findings was how strongly time in trade predicted pathogen sharing.<\/p>\n \u201cThat time-in-trade effect is the smoking gun,\u201d he said. \u201cWe wouldn\u2019t see that unless pathogens were jumping from animals to humans.\u201d<\/p>\n