Retroviruses of Bats: a Threat Waiting in the Wings?

Bats are infamous reservoirs of deadly human viruses. While retroviruses, such as the human immunodeficiency virus (HIV), are among the most significant of virus families that have jumped from animals into humans, whether bat retroviruses have the potential to infect and cause disease in humans remains unknown. Recent reports of retroviruses circulating in bat populations builds on two decades of research describing the fossil records of retroviral sequences in bat genomes and of viral metagenomes extracted from bat samples. The impact of the global COVID-19 pandemic demands that we pay closer attention to viruses hosted by bats and their potential as a zoonotic threat. Here we review current knowledge of bat retroviruses and explore the question of whether they represent a threat to humans.