The IHN virus has been discovered recently in farms on both the inside and the outside of the Island. It is obviously broadly distributed this year by an as of yet unidentified mechanism. Atlantic Salmon are the proverbial canaries in the coal mine for this disease though they do not distribute it because it's detection by specific and required farm disease monitoring always results in an immediate and complete cull of all stocks on the farm. The recent infections and consequent culls do, however, make it clear that the virus is present beyond normal prevalence this year and give some idea of the breadth and timing of the distribution mechanism.
Sockeye are known to be carriers of IHN and can be infected by it. When infected, they will shed viral particles along the routes they travel. BC Sockeye migrate on both the inside and outside of the Island to their home redds where they will spawn from their ocean residence period in North Pacific waters where Alaskan salmon also rear along with Japanese and Russian salmon. Herring are also susceptible to the virus and the disease it causes and can spread it.
The virus can be vertically transmitted to the next generation by infected breeding fish in both the hatchery or the wild.
Returns of Sockeye are so low this year that there is likely to be a complete closure to commercial fishing for them in the Fraser this year.
The recent discoveries may be an indication that we have a real problem and one that has absolutely nothing to do with farms.