Picobirnavirus: how do you find where it’s hiding?

Picobirnaviruses (PBVs) are double-stranded RNA viruses detected in various environments and host-associated samples, including those from humans, non-human animals, invertebrates and birds. First described in human fecal material, PBVs were initially hypothesized to be human enteric pathogens. However, no definitive association with disease has been established. Their pathogenic potential remains unclear, therefore, their presence in clinical or environmental samples may reflect asymptomatic colonization, indirect association or infection of a non-human host. The PBV genome exhibits remarkably high genetic diversity both within and across its genomic segments, as well as notable variability in genetic code usage. Some PBV genomes use alternative codon assignments, raising the possibility that they infect prokaryotic or otherwise unconventional hosts. This review critically examines the experimental and bioinformatic methods used to detect PBVs and infer their host range. We distinguish between methods used for PBV genome identification (e.g. PCR, metagenomic sequencing) and those aimed at host determination (e.g. culturing attempts, codon usage bias, cloning into model systems). We also evaluate the challenges and limitations associated with each approach. Elucidating PBVs' host range is essential to understanding their biological roles and ecological significance, including potential implications for human and animal health and microbial community dynamics across ecosystems.