 Pycine or thoriovirus genotype 1, or PRV1, is a virus known to cause inflammation of the heart and skeletal muscle in farmed Atlantic salmon. That has raised concerns among residents of the North American West Coast. Are Pacific salmon at high risk of disease from PRV1? New scientific evidence suggests no, at least for one strain of the virus. A team of researchers from the US, Canada and Norway injected three species of fish with tissue from Atlantic salmon testing positive for PRV1, Chinook salmon, Coho salmon, and rainbow trout. This method of infection is known to cause the hallmark symptoms of heart and skeletal muscle inflammation. These symptoms include severe heart inflammation, a low-reb blood cell count, and the formation of inclusion bodies in blood cells. The team sampled infected and control fish at regular intervals to assess levels of viral RNA, the relative number of red blood cells in blood and any signs of inclusion bodies or diseased tissues visible under a microscope. RNA analyses revealed that PRV1 replicated in 100% of infected fish across all three species, but in no case was infection with the virus associated with any notable mortality. The team did observe a few inclusion bodies in fish infected with PRV1, and at certain time points the proportion of red blood cells dipped for infected fish relative to controls. But no fish showed definitive signs of anemia, and no lesions consisted with severe inflammation were observed. All together, the results suggested that while all three species of North Pacific fish are susceptible to PRV1, infection did not cause significant disease. Yet the authors note that they looked at only the early freshwater life stages of these salmon. In addition, while PRV1 is currently the only strain of the virus known to exist in western North America, other strains have been reported in other areas of the world, including Europe and Japan. So while their results might rule out severe disease for certain fish infected with PRV1, the team urges management agencies to be cautious. Introducing exotic strains of PRV could have a vastly different effect on North American wildlife and aquaculture.