A lethal and highly contagious marine virus has been detected for the first time in wild salmon in the Pacific Northwest, researchers in British Columbia said on Monday, stirring concern that it could spread there, as it has in Chile, Scotland and elsewhere.

Farms hit by the virus, infectious salmon anemia, have lost 70 percent or more of their fish in recent decades. But until now, the virus, which does not affect humans, had never been confirmed on the West Coast of North America.

The researchers, from Simon Fraser University and elsewhere, said at a news conference in Vancouver that the virus had been found in 2 of 48 juvenile fish collected as part of a study of sockeye salmon in Rivers Inlet, on the central coast of British Columbia. The study was undertaken after scientists observed a decline in the number of young sockeye.