Bat-borne virus diversity, spillover and emergence

Abstract

Most viral pathogens in humans have animal origins and arose through cross-species transmission. Over the past 50 years, several viruses, including Ebola virus, Marburg virus, Nipah virus, Hendra virus, severe acute respiratory syndrome coronavirus (SARS-CoV), Middle East respiratory coronavirus (MERS-CoV) and SARS-CoV-2, have been linked back to various bat species. Despite decades of research into bats and the pathogens they carry, the fields of bat virus ecology and molecular biology are still nascent, with many questions largely unexplored, thus hindering our ability to anticipate and prepare for the next viral outbreak. In this Review, we discuss the latest advancements and understanding of bat-borne viruses, reflecting on current knowledge gaps and outlining the potential routes for future research as well as for outbreak response and prevention efforts.

Fig. 1. Currently described bat virus diversity.

Publicly available genetic sequence data for bat-derived viruses (database of bat-associated viruses) were pooled and categorized by viral family. Of note, large parts of the bat virus diversity remain uncharacterized, and discovery efforts have prioritized virus families with known zoonotic potential such as the Coronaviridae. ssDNA, single-stranded DNA.

Fig. 2. Overview of molecular host species barriers.

Viruses rely on numerous interactions with the host cell machinery in order to replicate and transmit. Virus–host interactions occur at every stage of the viral life cycle, including attachment, uncoating, genomic replication and protein expression, viral assembly and egress. While many factors involved are still unknown, some well-described examples are indicated. ER, endoplasmic reticulum; miRNA, microRNA.

Fig. 3. Using functional viromics to move beyond zoonotic virus discovery.

Current viromics research, mostly based on the targeted amplification of viral sequences or sometimes metagenomics, stops after the identification of novel viral sequences in animals. Large-scale functional screens of viruses in vitro will facilitate transmission and pathogenesis studies in vivo and ultimately lead to the development of ‘One Health’ intervention strategies, such as vaccination of humans or reservoirs or intermediate animal hosts, as well as other measures to reduce the risk of contact and viral transmission at the animal–human interface.