Contra Costa’s public health officer said in a press statement Friday that while the state Department of Public Health is monitoring a “very small” number of people who may have been exposed to hantavirus from the recent West Africa cruise ship outbreak, the wider public risk is “very low” because the virus isn’t easily transmitted between people.
The statement said local residents have expressed concerned and have been asking questions following reports of three deaths aboard a cruise ship near Cape Verde in the Atlantic. Hantavirus is a rodent-borne infection caused by exposure to the animal’s droppings or urine. It has only rarely been transmitted person-to-person.
“Contra Costa County has not been notified by the California Department of Public Health (CDPH) of any confirmed Andes hantavirus cases or exposure contacts in Contra Costa County,” the statement said, adding that health officials have received no information indicating that any of the monitored individuals in California are ill.
The CDPH said in a press release Friday that two California residents were aboard the MV Hondius, the cruise ship that experienced an outbreak of Andes hantavirus. One individual has returned to the state and is in contact with local public health officials regarding their exposure.
The second California resident is still on board the MV Hondius, the CDPH said, and the federal government is working to secure the safe return of all United States passengers.
The county health department is not recommending any special public health precautions or emergency preparations, noting that hantavirus infections in California are “very rare” and are from a strain that doesn’t spread between people and isn’t found in Contra Costa County. According to state health officials there have been 99 cases in the state between 1980 and 2025.
In one highly publicized 2011 case, a man died and a woman became seriously ill after contracting the disease at Yosemite’s popular Curry Village lodging area in Yosemite National Park. The man was the first person to die from hantavirus pulmonary syndrome contracted in the park, though two others were stricken in a more remote area in 2000 and 2010, officials said at the time. Testing by the Centers for Disease Control and the California Department of Public Health showed the virus was present in fecal matter from deer mice trapped in the tent community.
The cruise ship investigation involves the Andes strain of hantavirus, which may spread through prolonged close contact with an infected person.
Global health officials say risk to general public remains low
While the outbreak aboard a cruise ship has left three passengers dead and sickened others, global health officials say the risk to the general public remains low because the germ does not easily spread between people.
“This is not the next COVID, but it is a serious infectious disease,” said Maria Van Kerkhove, director of epidemic and pandemic preparedness at the World Health Organization. “Most people will never be exposed to this.”
The virus usually spreads when people inhale contaminated residue of rodent droppings. Hantaviruses have been around for centuries and are thought to exist around the world.
How to avoid hantavirus
People tend to contract hantavirus in the spring or early summer while doing spring cleaning or outdoor yard work. Ultraviolet light kills the virus so it’s recommended that one air out any closed up shed or similar space and wear protective gear while sweeping areas where rodents could be present.
Keep mice from nesting in the first place by caulking and rodent-proofing your home, and trapping mice that have already gotten inside.
Handwashing is important, as some transmission happens when people clean up, and then touch their mouth, nose or food they’re eating.
The disease gained renewed attention last year after the late actor Gene Hackman ’s wife, Betsy Arakawa, died from a hantavirus infection in New Mexico.
Detailed investigations of the cruise ship outbreak are ongoing, notably to determine its source.
Investigators in Argentina suspect that the cases were initially contracted during a birdwatching trip in Ushuaia, at the country’s southern tip, two officials told the Associated Press.
Argentina has seen a surge of hantavirus cases that many local public health researchers attribute to climate change.
Officials have found evidence of Andes virus, a version of hantavirus found in South America.
The virus is spread by rodents and, more rarely, people
Hantavirus is mainly spread by contact with rodents or their urine, saliva or droppings, particularly when the material is disturbed and becomes airborne, posing a risk of inhalation.
People are typically exposed to hantavirus around their homes, cabins or sheds, especially when cleaning enclosed spaces with little ventilation or exploring areas with mouse droppings.
Scientists are still trying to learn exactly how the Andes virus may be able to spread between people, said Dr. Jeanne Marrazzo, chief executive officer of the Infectious Diseases Society of America. They suspect people could be infectious when they have symptoms, and, if the virus spreads, it may be transmitted through small liquid particles that blow out of an infected person when they talk, cough or sneeze.
An infection can rapidly progress and become life-threatening. Experts say it can start with symptoms including fever, chills, muscle aches and maybe a headache — much like the flu.
Symptoms of hantavirus pulmonary syndrome usually show between one and eight weeks after contact with an infected rodent. As the infection progresses, patients might experience tightness in the chest, as the lungs fill with fluid.
The other syndrome caused by hantavirus — known as hemorrhagic fever with renal syndrome, which can cause bleeding, high fever, and kidney failure — usually develops within a week or two after exposure.
Death rates vary by which hantavirus causes the illness. Hantavirus pulmonary syndrome is fatal in about 35% of people infected, while the death rate for hemorrhagic fever with renal syndrome varies from 1% to 15% of patients, according to the CDC.
Infections have been relatively uncommon
Hantavirus infections are relatively uncommon globally. The WHO reported that in 2025, eight countries within the Americas had documented 229 cases and 59 deaths.
Argentina’s health ministry said hantavirus led to 28 deaths nationwide last year. The ministry on Tuesday reported 101 hantavirus infections since June 2025, roughly double the caseload recorded over the same period the previous year.
In the U.S., federal health officials began tracking the virus after a 1993 outbreak in the Four Corners region — the area where Arizona, Colorado, New Mexico and Utah meet. It was an astute physician with the Indian Health Service who first noticed a pattern of deaths among young patients.
Most U.S. cases are in western states. New Mexico and Arizona are hot spots, likely because the odds are greater for mouse-human encounters in rural areas.
The family of hantaviruses is named for the Hantaan River in Korea, where the first one was discovered.
That virus, called the Hantaan virus, infected 3,000 soldiers during the Korean War in the 1950s, causing a disease called Korean hemorrhagic fever. It killed 190 of them. The virus itself was not identified until more than 20 years later.
Hantaviruses have not been found to spread from person to person — with the possible exception of the Andes virus, which has been confirmed in the current outbreak.
Still, transmission between people does not happen easily, and would require “close and prolonged” contact, according to the WHO.
“We haven’t had huge person-to-person spreads of hantavirus infection ever before, and there’s no reason to suspect a huge outbreak from this case at this point,” said Steven Bradfute, an associate professor and associate director of the Center for Global Health at the University of New Mexico Health Sciences Center, which specializes in hantavirus research.
There is no specific treatment or cure, but early medical attention can increase the chance of survival.
Associated Press journalists Mike Stobbe and Randy Herschaft in New York and Isabel Debre in Buenos Aires, Argentina, contributed to this report.
