Global fragmentation of ecosystems and changing patterns of rainfall have increased the risk of diseases spreading to humans from animals, mosquitoes and ticks, finds a study co-led by a University College London (UCL) researcher.
The authors of the new Nature paper say they found a clear “anthropogenic fingerprint” on the global geography of emerging infectious diseases in humans, while also showing that the factors driving outbreaks vary substantially between different diseases.
An international team of scientists conducted the largest data-driven assessment to date of the environmental drivers of emerging infectious diseases, analysing 58,318 outbreaks across 32 diseases and 169 countries. They focused on outbreaks of diseases that are transmitted directly from animals – zoonotic diseases such as coronaviruses, Ebola and mpox – and vector-borne diseases transmitted by mosquitoes, ticks and fleas, such as dengue, Lyme disease and malaria.
The researchers found that outbreak risk was generally higher in areas where people and livestock live close to highly fragmented and forested ecosystems – for example, a forest that has been split up into many smaller woodlands separated by human settlements or farms. This is partly because animals that tend to thrive in such areas are more likely to carry diseases, and people are more likely to encounter them.
For vector-borne diseases, there was particularly clear evidence of human influence on the causes of their rising threat to global public health. Fragmented ecosystems, and areas experiencing long-term declines in rainfall due to climate change, saw increased risks of outbreaks of diseases such as dengue and Zika.
But for zoonotic infections (those that “spill over” directly from animals to people), including many pandemic threats, there were no environmental factors that consistently helped to predict where outbreaks occur. Instead, the effects of factors like deforestation, climate warming and agricultural intensification varied considerably between diseases. The researchers say that disease-specific and region-specific data are needed to monitor potential outbreak risks.
The scientists say their findings challenge the idea that there is a common set of environmental drivers behind the rise in emerging infectious diseases.
The research also demonstrates the critical role of healthcare access in determining where outbreaks are detected. The odds of emerging disease outbreaks being reported fell by an average of 32% for every additional hour of travel to the nearest healthcare facility. This suggests that apparent disease “hotspots” mostly reflect where disease surveillance and healthcare systems are currently strongest, rather than where infections are necessarily most common.
The authors call for a more proactive and holistic approach to preventing epidemics and pandemics, combining strengthening of health systems, global coordination of disease surveillance and ecosystem-based interventions for important diseases.
Lead author Dr Rory Gibb ( UCL People and Nature Lab ) said: “Our findings show that no single environmental recipe can predict where emerging infectious disease outbreaks will occur. Disease transmission from animals to people is common in human-modified habitats worldwide, but the exact human activities that drive outbreaks differ between diseases.
“This means that improving people’s access to healthcare and strengthening disease monitoring systems is critically important, to help make sure that outbreaks of any disease can be detected early and stopped before they become epidemics or pandemics.”
The study team was led by scientists at UCL, the University of Florida and Yale University, and the research was supported by a US National Science Foundation Biology Integration Institute grant to the Verena Institute.
Co-author Professor Sadie Ryan (University of Florida) said: “Spillover disease outbreaks are multi-causal, shaped by the socioecological system; this really highlights the need for One Health integrated approaches to surveillance and intervention – there is no single intervention strategy.”
Nature
The anthropogenic fingerprint on emerging infectious diseases
23-Sep-2026