Bats: Victims of Slander
In a groundbreaking scientific article published in Biology Letters, an international team of biologists, virologists, and environmentalists—including Sébastien Puechmaille of the Montpellier Institute of Environmental Sciences (Isem)—challenges the common belief that bats, particularly those in Africa, are the source of a myriad of viruses harmful to humans. Contrary to popular belief, this in-depth review of published studies provides little substantial evidence—apart from the Marburg and Sosuga viruses—that African bat species serve as reservoirs or intermediate hosts for viruses that spread to humans and cause serious diseases.
The scientific community and the general public have often been confronted with portrayals of bats as carriers of numerous dangerous viruses transmitted to humans. However, the research team, led by Natalie Weber, conducted a comprehensive and critical review of the available literature, focusing specifically on viruses detected in bats in Africa. They meticulously reviewed 162 articles published between 1978 and 2020 and, based on data from more than 80,000 individuals belonging to over 167 bat species, no substantial evidence was found that any bat species other than the Egyptian fruit bat plays a central role in virus transmission to humans in this region.
“The aim of our study was to provide a balanced, evidence-based assessment of the available knowledge regarding bat viruses and their relevance to the transmission of bat viruses to humans in Africa. “After a meticulous review and analysis, we found no convincing evidence to support the prevailing view that bats harbor a large number of viruses that are transmitted to humans. On the contrary, our results reveal only two bat-virus systems in which transmission is clearly documented,”says Natalie Weber.
A more nuanced approach
The researchers systematically reviewed the available data and determined which bat species were sampled, how frequently, and in which countries; whether they were sampled using lethal or non-lethal methods; what metadata was collected; and which viruses were detected using which methodologies. The results of these analyses challenge not only the scientific community but also the general public’s perception of bats, highlighting the importance of evidence-based understanding. DeeAnn Reeder, a co-author of the study, notes that“the results underscore the need for a more nuanced and better-informed approach to public discourse on the role of wildlife in disease emergence.” The authors therefore propose a framework to facilitate the standardized assessment of virus hosts in the future and call for greater interdisciplinary collaboration in studies of bats and viruses.
This review also revealed that misidentifications of bats and the use of outdated species classifications were common in published studies on viruses. Yet species identification is of great importance for follow-up investigations, particularly when a specific bat is identified as the host of a virus of interest. Furthermore, bats are often viewed as a single entity, but it is crucial to recognize the substantial diversity within this group, which has diversified over tens of millions of years; Africa alone is home to no fewer than 324 different bat species.
“When examining the relationship between bat species and viruses, precision in language is vital. Instead of making a general statement that ‘bats harbor the Marburg virus,’ it is more accurate to specify that ‘the Egyptian fruit bat, a specific bat species, harbors the Marburg virus.’ This concise approach maintains accuracy and avoids mistakenly associating all bat species with the Marburg virus,”explains Sébastien Puechmaille, co-author of the study and researcher at the Institute of Evolutionary Sciences in Montpellier.
Cautious communication
As emerging infectious diseases continue to raise global concerns, researchers hope that their work will contribute to a better understanding of the complex dynamics between wildlife—particularly bats—and human health. Their study also raises concerns about the impact of repeated reporting of research linking bats to viruses—based on insufficient evidence—on public perceptions of bats, as well as on human-bat conflicts and bat conservation efforts.
“Fear and active persecution of bats are increasing significantly, and populations are likely to decline across Africa. Careful, science-based communication of the findings, along with a balance between potential risks and benefits, will be essential to enable humans and bats to live side by side in our changing world,”says Dina Dechmann, co-author of the study. The implications of this research extend beyond Africa, encouraging a more thoughtful and evidence-based approach to the study of zoonotic diseases worldwide.