The eight became ill after eating oysters imported by Fortuna Sea Products Inc. at a private event in Woodburn, Ore., the Food and Drug Administration said Tuesday.
Norovirus causes nausea, vomiting, diarrhea and cramps sometimes accompanied by fever, chills, headache and muscle aches. It typically lasts one to two days.
The virus was traced to raw frozen oysters on the half shell imported from South Korea, the FDA said. On Nov. 27, California-based Fortuna recalled 1,100 cases of the South Korean oysters, which were distributed in Texas, Colorado, Nevada, California and Oregon.
A telephone message left with company spokesman John Chiang was not immediately returned Tuesday. A woman at the company said he would not be available until Wednesday.
The FDA said the federal Centers for Disease Control and Prevention was assisting in the investigation.