An analysis of more than 58,000 outbreaks of 32 diseases in 169 countries finds that the fragmentation of ecosystems and climate change–related declines in rainfall have driven up the risk of diseases that spread from animals, mosquitoes, ticks, and fleas to people.
For the study, published yesterday in Nature, an international group of researchers assessed outbreaks of zoonotic diseases (those transmitted directly from animals to people) such as coronaviruses, Ebola, and mpox and vector-borne diseases (those spread by mosquitoes, ticks, and fleas), including dengue, Lyme disease, and malaria.
Using data from published scientific datasets and national notifiable-disease surveillance systems from the United States, Brazil, and Argentina, the team systematically tested how 16 hypothesized social and environmental factors influence where outbreaks occur.
“Human-driven ecosystem changes and human–wildlife–livestock contact can drive the emergence of zoonotic and vector-borne diseases, but how much these processes shape landscapes of outbreak risk is poorly understood, beyond a few well-studied systems,” the researchers wrote.
No environmental factor helped predict sites of zoonotic outbreaks
In general, outbreak risk was generally higher in areas where people and livestock live close to fragmented and forested ecosystems (eg, a forest that has been split into smaller plots separated by residential areas or farms). This is partly because people in these areas are more likely to encounter the animals that tend to thrive in such environments, which are more likely to carry diseases.
The evidence of the connection between human influence and the rising threat to global public health was especially strong for vector-borne diseases, with increased risks of disease outbreaks from dengue and Zika virus in areas with fragmented ecosystems and declining rainfall.
