Study reveals human impact on global patterns of emerging infectious diseases

Human activities are helping shape where new infectious diseases emerge, according to a new study co-led by University of Florida medical geographer Sadie Ryan, Ph.D.

Published in Nature, the study analyzed 58,318 outbreak events involving 32 diseases across 169 countries, making it one of the largest data-driven assessments of the environmental and social conditions may influence disease outbreaks.

Ryan co-led the international research team with scientists from University College London and Yale University. The UF team also included geography postdoctoral associate Catherine Lippi, Ph.D., and Jason Blackburn, Ph.D., professor and chair of the Department of Geography. Both Ryan and Blackburn are principal investigators with UF’s Emerging Pathogens Institute.

The researchers found that outbreaks were most common in areas where people and livestock live alongside forests and other changing landscapes. These conditions, along with long-term declines in rainfall, were especially important for diseases spread by mosquitoes and ticks, including dengue and Lyme disease.

However, the study also found that the factors linked to disease outbreaks differ from one disease to another. For diseases transmitted directly from person to person, such as Ebola, mpox and coronaviruses, the researchers found few environmental factors that consistently predicted where outbreaks would occur.

“Spillover disease outbreaks are multicausal, shaped by the socioecological system,” Ryan said. “This really highlights the need for One Health integrated approaches to surveillance and intervention. There is no single intervention strategy.”

The study also revealed that access to health care was also a major influence on where outbreaks are reported. Reports of outbreaks fell 32% for every additional hour people had to travel to reach the nearest health care facility, suggesting that some outbreaks may go undetected in places with limited health care access and disease monitoring.

The researchers say that better health care, stronger disease monitoring and approaches tailored to specific diseases and regions will be important for detecting new threats and preventing outbreaks from spreading.