An American study which suggests that Heart & Skeletal Muscle Inflammation (HSMI) is caused by a virus, has triggered fears that the disease could spread to wild fish. HSMI is a fatal disease found among farmed salmon at more than 400 sites in Norway, and also found on farms in Scotland.

In a study published in the open-access journal PLoS ONE, a team led by W. Ian Lipkin, Director of the Center for Infection and Immunity at Columbia University's Mailman School of Public Health found that the disease may be caused by a previously unknown reovirus, a form of double-stranded RNA viruses that infect a wide range of animals.

The team – which included investigators from Norway – looked for viral sequences in heart and kidney samples taken from fish that were suffering from HSMI and healthy farmed salmon. They found evidence of the virus in 96.5% of the HSMI samples and none of the healthy fish.

A spokesman for Marine Scotland Science said that as yet it had found no evidence of HSMI. "It's relatively unusual to pick up pathogens in wild fish, apart from parasites and occasionally bacterial infections," the spokesman added. "We very occasionally pick up a viral pathogen, IPNv has been found in wild fish. But our routine surveys are part of a research programme within Scotland, and we will continue to monitor the health of wild fish stocks on an ongoing basis."