According to the Santa Clara County Public Health Department, the passenger was exposed and has returned home.
The county is monitoring and evaluating the person in coordination with the California Department of Public Health and the CDC.
According to Dr. Abraar Karan with Stanford University Infectious Diseases, health officials have a lot of information about the virus, and they know what they are up against.
"We know who we are monitoring, we know what virus we are dealing with," Karan said. "In this case, where we know this person was exposed, they are under quarantine. I don't expect that they will transmit to anybody else -- even if they develop symptoms, because at that point, they would be isolated."
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The California Department of Public Health is working with federal and local health officials to keep a close eye on the two Californians who were aboard the cruise ship that experienced an outbreak.
State public health officials issued a statement that said: "One person has returned home and is in contact with public health officials. And least one other remains on board the ship."
According to the cruise operator, passengers still on the ship do not have any symptoms of a possible infection.
Karan explained what happens next.
"The person will be under quarantine protocol, ideally until the incubation period has passed, which can go anywhere up to 40 to 42 days at longest," Karan said.
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Dr. Erica Pan, CA Public Health officer and CDPH director stated: "Unlike influenza and COVID-19, years of experience in South America have show that this Andes hantavirus rarely spreads between people."
According to CDPH, health officials are checking daily and monitoring the symptoms of the passenger that returned home to Santa Clara County.
This past week, ABC7 Eyewitness News caught up with travelers getting ready to set sail on their cruise from San Francisco.
Most took the news in stride.
"I think we're pretty OK. Obviously, you want to be careful because it's close quarters," said Jessica Ochoa-Briese.
"(We're hoping) just to be able to enjoy ourselves, not be stressed and worried about 'Am I going to get anything'," said Frances Ray Barnes.