Four California residents who may have been exposed during the deadly hantavirus outbreak tied to a cruise ship are now under monitoring, state health officials said Monday, while stressing that the threat to the public remains extremely low.
California State Public Health Officer Erica Pan, director of the California Department of Public Health, said three of the individuals had been passengers aboard the cruise ship MV Hondius. A fourth person was exposed on a commercial flight before the plane departed.
“We understand public concern about this unusual outbreak,” Pan said. “Decades of experience in South America have shown that this Andes hantavirus rarely spreads between people. We continue to work with federal and local officials to monitor the health of potentially exposed individuals and prepare for our Californians to come home.”
Last week, federal officials confirmed that three California residents had been aboard the cruise ship. On Friday, the California Department of Public Health announced that one California resident had returned home and was being monitored by public health officials, while the other two individuals were transported to a secure federal health facility in Nebraska.
Over the weekend, the U.S. Centers for Disease Control and Prevention informed state officials about another person now under active monitoring after possible exposure to a confirmed case during a shared flight. That individual is also staying at home while being monitored by their local health department.
Officials expect those staying at the federal facility to return to California after completing health evaluations and once plans are in place to protect both their health and public safety.
Current public health monitoring protocols include daily temperature checks, screening for symptoms associated with hantavirus, and instructions to limit activities such as going out, interacting with others, and leaving home except when necessary, along with other precautionary measures.
“The risk to the general public is extremely low right now,” Pan said.
She noted that the hantavirus outbreak may remind people of the coronavirus pandemic, but stressed that there are major differences. Pan said health experts have spent decades studying and responding to hantavirus outbreaks in South America, unlike COVID-19, which emerged as a completely new virus that scientists were still learning about in real time.
“If you are a contact and you are flying and you have no symptoms, you are not infected and you are not infecting anyone else,” Pan said. “All of our knowledge to date shows that in order to infect other people, you have to be ill. You have to have symptoms, so there’s no concern that a contact could infect other people.”
Pan said that before officials began responding to this outbreak, the CDPH Viral and Rickettsial Disease Laboratory was the only public health lab in the United States with a validated hantavirus PCR diagnostic assay, a testing tool used to detect hantavirus infections.
Pan added that if any exposed person develops symptoms linked to infection, California has the ability to conduct testing within the state. The CDPH VRDL is also helping laboratories nationwide by providing technical assistance to expand testing capacity.
Hantavirus refers to a group of viruses spread through the urine, feces, and saliva of wild rodents. These viruses include both the Sin Nombre and Andes strains. State health officials said the Andes hantavirus connected to the cruise ship outbreak is commonly found in the southern Andes regions of Argentina and Chile.
Health officials have also linked the Andes hantavirus to rare cases of person-to-person transmission after close and prolonged contact with someone who is infected and ill.
The Andes hantavirus differs from the Sin Nombre hantavirus, which is native to California and other parts of North America. Officials have not linked the Sin Nombre strain to person-to-person transmission.
According to the CDPH, 99 California residents were diagnosed with Sin Nombre hantavirus infections between 1980 and 2025.
Hantavirus Pulmonary Syndrome is a rare but serious respiratory illness that can develop after exposure. Early symptoms often resemble the flu and may include gastrointestinal issues before rapidly progressing to severe and potentially life-threatening respiratory distress. The fatality rate is estimated at 30% to 40%.
There is currently no antiviral treatment for hantavirus, and patients with HPS generally require intensive supportive medical care.