What drives large-scale epidemics of zoonotic diseases?


Since 1974, contaminated water has been the most common driver of large-scale zoonotic infectious disease outbreaks, according to new research from the Center for Infectious Disease Ecology (CEID) at the University of Georgia. The next two main factors are unusual weather conditions and changes in the abundance of disease vectors such as mosquitoes and ticks.

Zoonotic diseases occur when pathogens are transmitted from animals to humans. The most significant recent epidemics include Ebola hemorrhagic fever and COVID-19. However, most zoonotic epidemics involve fewer than 100 cases and are quickly brought under control. So what are the factors behind large-scale epidemics?

In a study published in the Royal Society’s Philosophical Transactions B journal, researchers investigated more than 4,400 zoonotic infectious disease outbreaks. They identified the top 100 in terms of the number of human cases, all of which have infected thousands to hundreds of thousands of people. From the full list, they also selected 200 random outbreaks to serve as “control cases”. The majority of these control outbreaks included 43 or fewer cases. They then compared the characteristics of large-scale and control epidemics, particularly how the main causes of infection and disease spread varied between them.

Lead author Patrick Stephens, associate researcher at Odum School of Ecology and CEID, said this research is one of the first peer-reviewed studies to quantify the variation in infectious disease outbreak factors across the world.

“In the era of COVID-19, it is understandable that many people may not realize how many outbreaks of other infectious diseases are caused by complex and intertwined ecological and socio-economic conditions,” he said. declared. “We know that factors such as exposure to wild mammals, habitat disturbance, international trade and travel, and contact with contaminated food and water are important considerations. Our research was designed to understand what proportion of epidemics various factors contributed. To our knowledge, this study is the first to do so for a global sample of epidemics of many diseases. “

Stephens worked with CEID researchers Nicole Gottdenker of the College of Veterinary Medicine and John Drake, Annakate Schatz and John Paul Schmidt of the Odum School to compile a list of contemporary zoonotic infectious diseases documented in the peer-reviewed scientific literature. They identified and scored 48 specific infectious disease factors linked to large-scale epidemics and control in ecological, environmental and socio-economic categories.

Water contamination is a key factor in epidemics

Large-scale outbreaks and control outbreaks were associated with water contamination, which was the most common driver of large outbreaks and the second most common driver of smaller control outbreaks. Examples of these water-associated illnesses include hepatitis E, typhoid, and shigellosis (dysentery). The remaining pilots differed, however.

In addition to water contamination, large epidemics were most often associated with unusual weather conditions, changes in the abundance of vectors (carriers of diseases such as mosquitoes or ticks) and water management. worn.

Large outbreaks were also much more likely to be caused by viral pathogens such as the SARS coronavirus, influenza virus, and Japanese encephalitis virus than smaller outbreaks. Typical smallest outbreaks were associated with food contamination, local animal production, and human-animal contact. Finally, large individual epidemics tended to be driven by a wider variety of factors than control epidemics.

“There is still a lot of work to be done to understand how large-scale infectious disease outbreaks can be avoided and controlled, Stephens said. “Perhaps two-thirds of future infectious disease outbreaks are expected to be caused by zoonotic pathogens, and the numbers of these diseases are increasing worldwide. Our research is an extremely important first step to better understand the global variation in the drivers of epidemics. “

Reference: Stephens PR, Gottdenker N, Schatz AM, Schmidt JP, Drake JM. Characteristics of the 100 largest modern zoonotic epidemics. Philos. Trans. R. Soc. Lond., B, Biol. Sci. 2021; 376 (1837): 20200535. do I: 10.1098 / rstb.2020.0535

This article was republished from the following materials. Note: The material may have been modified for its length and content. For more information, please contact the cited source.

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