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A study conducted at the Department of Ecology and Evolution of the University of Lausanne 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.
The global wildlife trade – especially in illegal and live-animal markets – is fueling the spread of diseases from animals to humans, according to a new study. The findings show that traded mammals are more than 40% more likely to harbor human-infecting pathogens, with species accumulating more shared pathogens the longer they remain in the trade. Close interactions between humans and wild animals create pathways for the spread of parasites and pathogens, sometimes triggering epidemics and pandemics. The global wildlife trade, which encompasses hunting, breeding, transport, retail, and pet ownership, poses particularly high risks of animal-to-human pathogen spillover. This trade has been linked to outbreaks ranging from HIV and Ebola to COVID-19 and mpox. While research has explored environmental and ecological factors that influence pathogen transmission, the dynamics of disease spread specifically within the wildlife trade and between humans and traded animals remain poorly understood.
Jérôme Gippet and colleagues analyzed 40 years of global wildlife trade data drawn from the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), the Law Enforcement Management Information System (LEMIS), and the Dataset of Seized Wildlife and their intended uses (DSW) datasets. They then linked this to the CLOVER database, which catalogs over 190,000 mammal-pathogen associations, to identify which species are known to share pathogens with humans. Gippet et al. found that among the 2,079 mammal species involved in global trade, 41% were found to share at least one pathogen with humans, compared with only 6.4% of nontraded species, and that traded mammals are 1.5 times more likely to host pathogens transmissible to humans. According to the authors, this suggests that cross-species transmission is an inherent feature of wildlife trade. Species in live-animal markets and, to a lesser extent, those involved in illegal trade, host more pathogens than those traded solely as products or legally. What’s more, the findings show that the duration a species spends in trade further amplifies risk. Gippet et al. found that each decade a species is traded corresponds to one additional pathogen shared with humans, on average.
Punishing freeloaders in public good games (PPGs) – experimental models used to analyze the social dilemma between individual self-interest and group cooperation – can boost cooperation, but whether punishment helps or harms the groups’ outcomes depends heavily on context, according to a study involving over 7,000 human participants. The findings reveal when, rather than whether, punishment works. Human societies routinely confront so-called “social dilemmas” – situations in which individual incentives clash with the collective good. These scenarios can arise in contexts ranging from public health to environmental policy. When they occur, cooperation – or prioritizing shared benefit over personal gain – is both essential and difficult to sustain. PPGs offer a simplified model for examining these dynamics. Although the group benefits most when everyone contributes fully, individuals can maximize their personal gain by contributing nothing. One widely studied solution to this problem is costly peer punishment, where individuals penalize those who fail to contribute. While this mechanism can discourage selfish behavior, it comes at a cost to both punisher and punished. Past studies have shown that, in some cases, the burden of punishment outweigh its benefits. However, despite this body of research, the conditions under which punishment best promotes cooperation remains unclear.
To better understand these dynamics, Mohammed Alsobay and colleagues conducted a large integrative experiment, systematically varying 14 features of PPGs (e.g. communication, group structure, incentives) across 360 conditions, analyzing more than 147,000 decisions from 7,100 participants. According to Alsobay et al., the experimental design allowed them to precisely identify when punishment helps or hinder shared outcomes, which factors matter most, and how they interact. The authors found that punishment consistently increased cooperation, but its effect on collective welfare varied dramatically – from a 43% improvement to a 44% reduction – depending on context. According to the study, communication was the most influential factor and was roughly three times more consequential than any other variable. Other important elements include how contributions are framed, the structure of contribution choices, the duration of the interaction, and the visibility of others’ outcomes. Notably, the findings show that these factors do not operate in isolation but interact in complex ways. For example, longer interactions only enhance the effectiveness of punishment when communication is possible. The authors also used the data to develop and train a predictive model that was able to outperform humans when predicting whether punishment would help or harm welfare in new experiments.
Children who don’t go to the dentist are less likely to participate in school-based cavity prevention programs, according to research published in JAMA Network Open. In addition, the study found that improving participation in state-wide school dental programs to reach those at high risk for tooth decay could yield significant savings for state Medicaid programs and health care systems, averting up to $2.4 million in emergency department charges annually in New York.