Spillover of zoonotic pathogens: A review of reviews

The authors of this paper systematically reviewed a collection of 88 review papers from 10 disciplines with four distinct goals in mind. They wanted to describe key elements in main spillover processes, identify disciplines that discuss spillover and compare their foci, identify shared interest across disciplines, and summarize gaps in spillover knowledge that need increased research. This paper identified understudied areas and collaborative opportunities for the disciplines identified. The authors selected peer-reviewed studies using six databases (chosen for their broad range of topics and disciplines) and keywords relating to zoonotic disease, infecting and spillover. Papers were excluded if they had too narrow or broad a focus or if they discussed companion animals. 

The authors described both “pathways” (mechanisms for disease spillover from animals to humans) and “gaps” (questions or problems that review authors believe haven’t been properly addressed in literature). Authors of this review read their selected papers, identifying 68 common phrases, to be sorted into nine categories (adapted from a preexisting framework) along with the disciplines that the papers came from, then sorted them into clusters based on similarities. They used two network diagrams to find similarities between disciplines (one to see how often disciplines were assigned to the same paper, and the second to identify content that was similar across disciplines).  

The authors found 8 gaps in spillover process knowledge, general concepts, and research approaches. The gaps include climate influences on vectors, socioeconomic and behavioral factors, traits that allow a host to tolerate or transmit infection, traits that allow pathogens to spillover, changes in microbial communities, knowledge of past outbreaks, potential sources of human disease. The major gap was collaboration between academic disciplines, which would be useful to understand how complex zoonotic pathogen spillover is. 

The authors did identify limitations in their work (their codes, and methods of assigning disciplines and papers are subjective, creating room for bias), however, they were able to make suggestions. They suggest focusing on understudied clusters, pathogen diversity, and drawing on historical material. They also called for an increase in interdisciplinary collaboration.

The paper was accepted in the Zoonoses Public Health Journal on April 3, 2021. Zoonoses Public Health. 2021 Sep;68(6):563-577. doi: 10.1111/zph.12846.

Cecilia A Sánchez, Joy Venkatachalam-Vaz, John M Drake

Summary by Jannah Zinker