California is one of four states that are monitoring people who previously traveled on the MV Hondius cruise ship, where a cluster of hantavirus cases turned deadly.
People in California, Arizona, Georgia and Texas are being monitored for potential infection after previously being on the cruise ship, though none have shown signs of illness so far.
Health officials say about 30 passengers disembarked at different locations two weeks ago. Contact tracing is now underway for anyone who may have been exposed to sick patients earlier in the trip.
“There is no information that the California residents are ill or infected… At this time, the risk to public health in California is low,” the California Department of Public Health’s Robert Barsanti said in a statement.
So far, three passengers of the cruise ship have died.
The trip is expected to take three to four days, the ship’s operator, Oceanwide Expeditions, said Wednesday.
Some passengers disembarked the ship before knowledge of the cluster and are back in their home countries. In some cases, authorities are advising those passengers to self-isolate.
The total number of confirmed hantavirus cases aboard a cruise ship has risen to five as global health authorities work to contain a potentially deadly cluster of the disease.
More than 100 passengers remain on the ship, MV Hondius, and the World Health Organization (WHO) is monitoring their health. Officials said that the “overall public health risk remains low” but that there may be some person-to-person spread.
In its first public statement on the outbreak on Wednesday evening, the U.S. Centers for Disease Control and Prevention said, “the risk to the American public is extremely low” and urged Americans aboard the ship to follow the guidance of health officials.
What is hantavirus?
Hantavirus is a respiratory infection with no treatment and can kill up to 40% of those infected. The WHO says testing so far has identified the rare Andes strain of the virus, which can spread from person to person.
“That is the species that has been identified on the cruise ship. So that’s why they’re starting to worry more and more about the potential for person to person spread,” said Dr. Emily Abdoler, an infectious diseases physician.
How did it spread?
Health officials now suspect the first victim to contract the virus picked it up in Argentina before getting on the ship. In mid-March, he’d visited a landfill during a bird watching tour and officials suspect he contracted it from rodents.
The caption of the ship announced his death weeks ago, telling those on board the man wasn’t infectious before anyone knew it was hantavirus.
However, that man likely spread it to his wife, who also died.
ABC News contributed to this report.
