California Keeps an Eye on 4 Residents for Possible Hantavirus Exposure

California Residents Monitored for Hantavirus Exposure Linked to Cruise Ship

Four California residents are currently under observation following possible exposure to a hantavirus outbreak associated with the cruise ship MV Hondius, state health officials announced Monday. The California Department of Public Health (CDPH) emphasized that the risk to the general public remains extremely low.

State Public Health Officer Erica Pan confirmed that three of the individuals were aboard the MV Hondius, while the fourth was exposed during a commercial flight that had not yet taken off.

"We understand public concern about this unusual outbreak," Pan stated. "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 authorities identified three California residents aboard the cruise ship, prompting the CDPH to announce that one individual has already returned to the state. This person is being monitored by public health officials, while the other two have been transported to a secure federal health facility in Nebraska.

This weekend, the U.S. Centers for Disease Control and Prevention (CDC) informed state officials of an additional person undergoing active monitoring due to potential exposure on the same flight as a confirmed case. This individual is also at home and being closely monitored by their local health department.

The individuals housed at the federal facility are expected to return to California once health assessments are complete and arrangements have been made to safeguard both their health and the public’s health.

Current public health monitoring protocols include daily temperature checks and assessments for symptoms consistent with hantavirus. Exposed individuals have been advised to limit outings and interactions, remaining at home as much as possible.

"The risk to the general public is extremely low right now," Pan reiterated. She noted the differences between this outbreak and the COVID-19 pandemic, emphasizing that there is decades of research on hantavirus, as opposed to the rapid learning curve witnessed during the coronavirus outbreak.

"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 assured. "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."

According to the CDC, hantaviruses can lead to severe illness and even death. Prior to the current outbreak, the CDPH’s Viral and Rickettsial Disease Laboratory was the only public health laboratory in the U.S. with a validated hantavirus diagnostic PCR assay, capable of testing for hantavirus.

In the event that any exposed individuals develop symptoms reflective of infection, California is equipped to conduct testing. The CDPH VRDL is also assisting other laboratories nationwide to enhance testing capabilities.

Hantavirus is primarily transmitted through the urine, droppings, and saliva of wild rodents. The Andes hantavirus linked to the cruise ship outbreak is prevalent in the southern Andes region of Argentina and Chile. While human-to-human transmission is rare, it can occur through close, prolonged contact with an infected person.

Distinct from the Andes strain, the Sin Nombre hantavirus is native to California and has not been associated with person-to-person transmission. From 1980 to 2025, 99 California residents have been diagnosed with Sin Nombre hantavirus infection.

Hantavirus Pulmonary Syndrome (HPS) is a severe respiratory illness that may develop after exposure. Initial symptoms can resemble influenza, including gastrointestinal issues, and may progress rapidly to life-threatening respiratory distress. The fatality rate for HPS is estimated at 30% to 40%, and there is no antiviral treatment. Medical care typically requires aggressive supportive treatment.