Divergent coronaviruses discovered in the virome of lamprey with reddening syndrome.

Lamprey reddening syndrome (LRS) is an emerging disease affecting pouched lamprey ( IMPORTANCE: Lamprey are among the world's oldest living vertebrates and hold deep cultural significance for Māori as taonga species. An emerging disease causing skin reddening and death has raised concerns for their long-term conservation, but its cause has remained unknown. By applying genomic sequencing, we discovered a remarkable diversity of previously unknown viruses, including two highly unusual coronaviruses, in New Zealand and Australian lamprey. Rather than identifying a single disease-causing virus, our results suggest that disease is more likely associated with increased viral replication in stressed animals or with multiple infections acting together. These findings provide an important step toward understanding the health of this threatened species while also revealing unexpected viral diversity in an ancient vertebrate lineage. More broadly, the study demonstrates how genomics-informed diagnostics can help investigate unexplained disease outbreaks in wildlife and guide conservation management.