Rodents as Potential Reservoirs for Toroviruses

Abstract Emerging zoonotic viruses pose a significant threat to global health. The order Nidovirales includes diverse viruses, such as coronaviruses, which are well known for their zoonotic potential. Toroviruses are a less-studied genus within Nidovirales primarily associated with gastrointestinal diseases in ungulates, although some evidence suggests their presence in humans. In this study, we report the discovery of a novel torovirus from a fecal sample of a dormouse ( Eliomys quercinus ) in Spain, which we named Dormouse torovirus (DToV). This represents the first complete genome of a rodent-associated torovirus. The 28,555-nucleotide genome encodes the six characteristic torovirus open reading frames, but these exhibit low amino acid sequence identity (44.3–86.3%) compared to other toroviruses, indicating that DToV likely represents a new viral species. Bayesian analysis of the ORF1b suggests that DToV diverged from known toroviruses approximately 1300 years ago. Moreover, the basal phylogenetic position of DToV suggests that rodents may represent a reservoir for this viral genus. Our findings expand the known torovirus host range, underscore their potential for cross-species transmission, and highlight the importance of continued surveillance of wildlife viruses. Importance Currently, there is concern about the potential emergence of new viruses from natural reservoirs. This has led to an increasing search taking advantage of new massive sequencing methodologies. In our study, we have identified a complete genome of a torovirus in a rodent species in Spain. Toroviruses are a group related to coronaviruses and cause gastrointestinal diseases in ungulates, such as cows or pigs. However, they have not been studied in depth, as there is no clear evidence of their ability to infect humans. Our results suggest that rodents may be the natural reservoir of toroviruses and underline their potential for cross-species transmission. Based on the results obtained from monitoring wildlife for viruses with zoonotic potential, the next step will be to implement new approaches in the laboratory to characterise the ability of these viruses to infect humans.