Fractured ecosystems, climate change raise risk of zoonotic, vector-borne disease outbreaks, study finds
Mary Van Beusekom, MS50 minutes ago.
Climate Change
Dengue
Ebola
Lyme Disease
Malaria
Mpox
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.
Our findings show that no single environmental recipe can predict where emerging infectious disease outbreaks will occur.
Rory Gibb, PhD
But no environmental factor consistently helped predict where outbreaks will occur for zoonotic infections, including those caused by pathogens with pandemic potential. Rather, the effects of factors such as deforestation, climate warming, and agricultural intensification varied widely by disease. The researchers say that disease- and region-specific data are needed to monitor outbreak risks.
The scientists say their findings challenge the assumption that a common set of environmental factors is driving the rising risk of emerging infectious diseases.
“Our findings show that no single environmental recipe can predict where emerging infectious disease outbreaks will occur,” co-corresponding author Rory Gibb, PhD, of University College London (UCL), said in a UCL news release. “Disease transmission from animals to people is common in human-modified habitats worldwide, but the exact human activities that drive outbreaks differ between diseases.”
No single intervention strategy
The findings also illustrate the critical role of healthcare access in determining where outbreaks are reported. The probability of reporting an emerging disease outbreak fell by, on average, 32% for every additional hour of travel to the nearest healthcare facility. The authors said this finding suggests that apparent disease hot spots likely reflect areas with the strongest disease surveillance and healthcare systems rather than areas where cases are most common.“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,” Gibb said.
The researchers urge taking a more proactive and holistic approach to preventing epidemics and pandemics, strengthening health systems, and global coordination of disease surveillance and ecosystem-based interventions for important diseases.
“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,” co-corresponding author Sadie Ryan, PhD, of the University of Florida at Gainesville, said in the release.