Hantavirus is rare—only 728 cases have been reported in the U.S. since 1993. However, complications from a hantavirus infection can be deadly.

By Maggie O'Neill
March 25, 2019

Rodents invade about 21 million homes in the U.S. each winter, and they’ve pestered nearly one-third of Americans in their houses. Sometimes a rodent infestation is a quick-fix problem—if you set up some traps around the infested area, they might leave you alone soon enough. But if you have to clean up an area infested by rodents, you’re going to want to take some extra safety precautions: Some rodents in the U.S. can carry a disease called hantavirus that can potentially be deadly.

To be clear, your chances of getting the virus are quite slim. Since the U.S. started tracking the number of hantavirus cases in the country in 1993, only 728 have been reported. Health spoke to an expert to find out how to minimize your chances of getting the virus, which can be easily confused for pneumonia.

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Hantaviruses in the U.S. “are uncommon diseases, thankfully,” says Pritish Tosh, MD, an infectious disease researcher and physician at the Mayo Clinic. In order to be infected by one of the strains, “you have to have contact with a rodent that is carrying the virus,” he adds. “Being exposed to mouse droppings is the primary risk factor. The hantaviruses in the U.S. are not really spread person to person.” (Phew!)

The different types of hantaviruses have a “preferred rodent carrier,” according to the Mayo Clinic. For example, the deer mouse is usually responsible for spreading the type of hantavirus that results in hantavirus pulmonary syndrome (HPS), a severe form of hantavirus infection that typically involves fever, muscle aches, dizziness, and fatigue.

When hantavirus is inhaled, it invades blood vessels in your lungs called capillaries. Eventually, the virus causes your capillaries to leak, resulting in your lungs filling with fluid. Hantavirus symptoms include fever, fatigue, and muscle aches—especially in the thighs, back, hips, and sometimes the shoulders, according to the Centers for Disease Control and Prevention (CDC). Dizziness, chills, abdominal problems, and headaches affect about half of people diagnosed with HPS. Hantavirus pulmonary syndrome can also progress to involve shortness of breath.

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Dr. Tosh says symptoms of a hantavirus infection usually appear in less than a week, although it can take up to eight weeks after exposure to mouse droppings for hantavirus symptoms to surface. The rare illness is sometimes mistaken for pneumonia, which is much more common and also affects the lungs. But the chances of surviving HPS aren’t great: 38% of people diagnosed with HPS die due to complications from the disease, according to the CDC.

In August 2018, the North Dakota Department of Health announced the death of a resident who died from HPS after possibly coming into contact with rodent droppings or urine. “People need to be mindful of the presence or evidence of wild rodents or rodent nests when conducting clean-up activities in a house, barn, or other buildings, especially in rural areas,” an epidemiologist at the Department of Health said in a press release at the time. “It is important to avoid actions that stir up dust, such as sweeping or vacuuming, if signs of rodents are present.”

If you find yourself cleaning an infested area, be sure to cover your mouth and nose, as the main way hantavirus is spread in the U.S. is through inhalation of the virus. “If you are dealing with mouse droppings or mouse urine, you should be wearing some sort of respiratory protection if you are cleaning,” Dr. Tosh says, like a surgical mask.

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People living in rural western regions of the U.S. are most at-risk for getting hantavirus. In fact, more than 96% of reported HPS cases in the U.S. have occurred west of the Mississippi River, according to the North Dakota Department of Health.

If you live in these areas (or even if you don’t) you can also help prevent hantavirus infections by taking a few simple rodent-proofing steps. Make sure holes big and small in your home get sealed; mice can fit through spaces that are the size of a nickel, according to the CDC. Keep food—pet food included—in rodent-proof containers. Clear away brush and grass around your home; this will decrease the chances of mice nesting right outside your house. And set up spring-loaded traps along your baseboards to catch invading rodents.

Get more on infectious diseases here.

This post was originally published on April 27, 2018 and updated for accuracy.