A new global study has found that countries importing larger volumes of wildlife face a higher likelihood of emerging infectious diseases spreading from animals to humans. The findings suggest that wildlife imports, rather than exports, may play a more significant role in zoonotic disease emergence.
Published in the peer-reviewed journal One Health, the study was conducted by researchers at Xi’an Jiaotong-Liverpool University (XJTLU). It provides the first global assessment of the relationship between wildlife trade and zoonotic disease outbreaks across countries and over time.
Zoonotic diseases have emerged as a major public health concern following outbreaks of SARS, MERS, and COVID-19. Wildlife is linked to at least 70% of emerging zoonotic diseases, highlighting the importance of understanding how international wildlife trade contributes to pathogen transmission.
Researchers Examine Wildlife Trade Across 214 Countries
The research team analysed data from 214 countries spanning 39 years to investigate whether wildlife trade volumes were associated with emerging infectious disease (EID) occurrences.
The researchers used two statistical approaches. The first examined whether countries with higher wildlife trade volumes were more likely to report zoonotic disease occurrences and whether they experienced more such events. The second investigated whether unusually high wildlife trade volumes coincided with extreme disease outbreak events.
Both approaches separately assessed wildlife imports and exports.
Dr Lingyun Xiao, a corresponding author from XJTLU’s Academy of Life and Natural Sciences, explained that earlier research had examined factors such as economic conditions, population growth, and climate without directly assessing wildlife trade volumes.
“While previous papers have identified the spatial link between EID occurrences with other factors such as population growth rate, GDP, and climatic conditions, wildlife trade volumes remain untested,” Dr Xiao said.
The researchers also examined non-zoonotic emerging infectious diseases to determine whether the observed relationships could be explained by differences in disease surveillance or general trade activity.
“If wildlife trade were simply a proxy for general trade or reporting bias, we would expect it to be associated with non-zoonotic EIDs too,” Dr Xiao said. “The fact that the strongest and most specific signal was for zoonotic EIDs strengthens the case that this is not just reporting noise.”
Higher Wildlife Imports Linked to 23% Greater Odds of Disease Emergence
The findings revealed a significant association between wildlife import volumes and the likelihood of zoonotic emerging infectious disease occurrences.
The researchers reported an odds ratio of 1.23, indicating that a one-unit increase in the study’s wildlife import volume measure was associated with approximately 23% higher odds of a zoonotic EID occurrence.
However, wildlife exports showed no statistically significant association with zoonotic disease emergence.
Kai Wang, a PhD student at XJTLU’s Academy of Life and Natural Sciences, explained that importing wildlife could introduce unfamiliar pathogens into a country, increasing the possibility of transmission to humans.
The researchers also distinguished between the likelihood of disease emergence and the frequency of reported occurrences. Although wildlife imports were associated with an increased probability of zoonotic EID emergence, they were not significantly associated with the number of occurrences once an EID had emerged.
Other factors, including surveillance systems, containment measures, and public health responses, may influence the subsequent number of reported disease events.
Extreme Disease Outbreaks More Likely During High Wildlife Import Activity
The study also identified a relationship between unusually high wildlife import volumes and extreme zoonotic disease outbreak events.
According to the researchers, extreme zoonotic EID events were 40% more likely to coincide with high wildlife import volumes. The corresponding relationship for wildlife exports was substantially weaker.
Dr Chengxiu Ling, another corresponding author from XJTLU, highlighted the importance of these findings for understanding rare but potentially severe public health emergencies.
“This reveals a critical import-driven risk profile: wildlife importation is associated with both the probability of zoonotic EID occurrence and extreme outbreak events,” Dr Ling said.
The researchers also identified mammalian species richness, population density, and population growth as additional factors associated with elevated emerging infectious disease risks.
The findings indicate that wildlife imports may be particularly relevant to pandemic preparedness because rare, extreme outbreaks can have disproportionately large consequences for public health.
Study Calls for Stronger Wildlife Import Screening and Surveillance
Based on the findings, the researchers recommended strengthening disease prevention measures at wildlife import checkpoints.
These measures include improved quarantine procedures, pathogen screening, and public health surveillance targeting imported live wildlife.
The researchers explained that imported animals may introduce pathogens unfamiliar to local human populations, potentially increasing the risk of disease emergence.
Dr Ling also emphasised that the risks associated with wildlife imports appear to differ from those associated with exports.
“Exportation may reflect broader wildlife exploitation and increased human–wildlife encounters. But our findings suggest that zoonotic risk is more likely associated with the intensity of wildlife importation than with overall trade activity. That is why the policy focus should be on importation points.”
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