After an outbreak of hantavirus killed three people on a cruise ship in recent weeks, Google searches for the disease have increased by more than 1,000% in some states. In general, the virus is rare and difficult to contract for most people.
But that didn’t stop the disease from spreading to as many as 17 American passengers aboard the cruise ship. They arrived back in the U.S. on Monday, and will now be monitored at the National Quarantine Unit at the University of Nebraska Medical Center.
However, backpackers — and anybody who spends time in wooded areas — are actually at a higher risk of contracting the disease than cruise ship passengers. A few key prevention strategies can help keep you safe.
What Is Hantavirus?
Hantavirus is a general term for two types of syndromes brought on by this pathogen, according to the Centers for Disease Control (CDC). The first, which is more common in the Western Hemisphere, is Hantavirus Pulmonary Syndrome.
Initial symptoms include fatigue, fever, and muscle aches in the hips, back, and shoulders. About 4 to 10 days after the first phase, the lungs fill with fluid, prompting other symptoms like coughing and shortness of breath to develop. The disease can be deadly, with a 38% fatality rate.
The second type, hemorrhagic fever with renal syndrome (HFRS), is mostly found in Europe and Asia. Unlike HPS, it primarily affects the kidneys; symptoms include intense headaches, nausea, fever and chills, and blurred vision. Around 5–15% of cases are fatal. There is no vaccine for any strain of hantavirus.
Officials have not firmly identified a cause for the hantavirus outbreak on the cruise ship. That version, however, was a rare strain from the Andes that can spread from person to person.
How Do You Get It?
Human-to-human transmission is extremely rare. Infection primarily comes from contact with mice and rodents. It can spread to humans via airborne transmission if they have contact with mouse droppings, saliva, or urine.
“When fresh rodent urine, droppings, or nesting materials are stirred up, tiny droplets containing the virus get into the air,” Nevada’s Office of State Epidemiology (NOSE) stated. It’s possible to get it if you touch something that mice have pooped or peed on, and then you touch your nose or mouth.
There’s a risk of transmission even if you don’t notice any rodents. In about one-third of cases, infected patients reported never seeing any mice: “Scientists also suspect people can become sick if they eat food contaminated by urine, droppings, or saliva from an infected rodent,” NOSE said.
Symptoms of HPS typically begin to appear 1 to 8 weeks after contact with an infected rodent.
In Colorado, Nevada, and other Western U.S. states, the deer mouse, which prefers woodland habitats, is the most commonly cited rodent for human infections. Roughly 15% of deer mice are carriers of the disease. Transmission rates from those exposed to the infected mice can reach 40%.
How Common Is It?
From 1993 to 2023, the CDC has recorded 890 cases of hantavirus in the U.S, with a fatality rate of 35%.
Almost all of them resulted in Hantavirus Pulmonary Syndrome. The disease is particularly a problem in the American West: 94% of all of these cases originated west of the Mississippi River. New Mexico and Colorado are the states home to the most infections, with 129 and 121 reports, respectively.
Certain areas with high numbers of deer mice tend to produce more cases. Mono County in California, for example, has a large rodent population and has recorded 27 cases — the most in the state.
In April 2025, local authorities reported that three people had died from hantavirus in the town of Mammoth Lakes.
Risk Factors and Prevention
There are several occupations, spaces, and activities that can put someone in greater contact with mice, and thus at greater odds of contracting hantavirus.
People who work in construction or pest control, for example, are at a greater danger. In fact, the majority of exposures to the disease (70%) occur “around the home,” according to Washington State University. That underscores the potential danger for backpackers. Sleeping in cabins, shelters, or backcountry huts (prime environments for mice) means possible exposure to these disease-carrying rodents.
“The chance of being exposed to hantavirus is greatest when people work, play, or live in closed spaces where rodents are actively living,” according to Nevada’s epidemiology office.
To reduce your chances of infection, be sure to examine any hut, shelter, or cabin for signs of rodents before staying there. These include droppings, nesting materials, holes chewed through walls and floors, and musty odors. If you find evidence of mice, sleep elsewhere. Always store your food in rodent-proof containers. Make sure your tent is in good condition, and patch any holes or gaps.
It’s best to treat any rodent sighting as if you saw a deer mouse.
“All rodent exposures should be considered as potential Hantavirus exposures since deer mice may be present in the same environments as house mice, even if they aren’t seen,” Colorado’s Department of Public Health & Environment said.
If you need to clean gear or clothing that mice have touched, be sure to wear a mask and use gloves to handle the item. Then use a disinfectant or wash in hot water with detergent.
No matter where you contract the disease, hantavirus is not contagious between humans. But that doesn’t mean you can avoid quarantine measures. Two of the infected cruise ship passengers had to return to the U.S. in “specialized biocontainment units out of an abundance of caution,” The New York Times reported.
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