The outbreak has sickened at least 1,600 people in five states.
California health officials on Monday released new information about four residents who were exposed to the hantavirus and are now being monitored, all of whom are currently healthy and not showing symptoms.
The outbreak was reported to the CDC on Thursday, during the cruise ship's April 28 to May 11 voyage.
Spanish authorities on Friday were preparing to receive more than 140 passengers and crew members on board a hantavirus-stricken cruise ship headed for the Canary Islands.
The CDC has activated its Emergency Operations Center and classified a hantavirus outbreak as a Level 3 response, the agency's lowest level of emergency activation, signaling a low risk to the general public.
More than two dozen people from at least 12 different countries left a cruise ship hit by a deadly hantavirus outbreak without contact tracing, officials say