Robust evidence for bats as reservoir hosts is lacking in most African virus studies – a review and call to optimize sampling and conserve bats

Africa experiences frequent emerging disease outbreaks among humans, with bats often proposed as zoonotic pathogen hosts. We comprehensively reviewed virus-bat findings from papers published between 1978 and 2020 to evaluate the evidence that African bats are reservoirs and/or bridging hosts for viruses that cause human disease. We present data from 162 papers (of 1322) with original findings on (1) numbers and species of bats sampled across bat families and the continent, (2) how bats were selected for study inclusion, (3) if bats were terminally sampled, (4) what types of ecological data, if any, were recorded, and (5) which viruses were detected and with what methodology. We propose a scheme for evaluating presumed virus-host relationships by evidence type and quality, using the contrasting available evidence for Orthoebolavirus (formerly Ebolavirus) versus Orthomarburgvirus (formerly Marburgvirus) as an example. We review the wording in abstracts and discussions of all 162 papers, identifying key framing terms, how these refer to findings, and how they might contribute to people’s beliefs about bats. We discuss the impact of scientific research communication on public perception and emphasize the need for strategies that minimize human-bat conflict and support bat conservation. Finally, we make recommendations for best practices that will improve virological study metadata.

Methods
We analyzed data from peer-reviewed primary research articles published through 2020 for which bats were captured in Africa for viral surveillance. We used the search terms “bat OR bats OR Chiroptera” AND “virus OR viral OR virological” AND “Africa OR ‘each African country name in English or country name variant’” (Fig. S1) in a Web of Science (all database) search, repeated in French, yielding a total of 1322 papers (two from French search). We also included older primary data from seven studies used in 11 modeling papers from this period. In total 162 papers met our study inclusion criteria, published between 1978 and 2020 (Text S1). This dataset, analyzed alongside our current understanding of African bat systematics and ecology, provided a snapshot in time of African bat viral research from which we were able to describe the nature of these studies in detail (Fig. 1). Data on (1) numbers of species and individuals sampled across bat families and the continent; (2) how bats were selected for study; (3) whether they were terminally sampled; (4) whether ecological data were recorded; and (5) which viruses were detected and with what methodology, were manually extracted. We focus on four viral families most relevant to humans: Coronaviridae, Paramyxoviridae, Rhabdoviridae and Filoviridae, list other viral findings, and propose a schematic approach to evaluating the quality of the evidence underlying putative bat-virus relationships, using the contrasting available evidence base for Orthoebolavirus versus Orthomarburgvirus as an example. Our findings are placed in the context of numbers of known and suspected human infections and fatalities from African zoonoses associated with bats. Finally, we review the wording in abstracts and discussions of all 162 papers. We identify several key framing terms, how these refer to findings, and how they might contribute to people’s beliefs about bats. In light of the growing fear of bats as sources of viral spillovers, we discuss the impact of scientific research communication on public perception and emphasize the need for strategies that minimize human-bat conflict.