IHN is also a virus. We call it the sockeye disease because sockeye salmon tend to become infected. It can be devastating to that population. Other Pacific salmon have some tolerance of it, depending on which species we talk about. Atlantic salmon are incredibly susceptible to this disease.
I did the outbreak investigation and actually published a report on the last outbreak of IHN in British Columbia, which happened in 2000 to 2003 among farmed salmon. Basically, you can easily get mortalities of up to 80% and almost 100%. Farms have to be culled because of this disease. It's not a disease you can hide. Once a population becomes infected, you can definitely see it throughout.
So it's not a disease you can hide, and we basically haven't seen it since 2003.