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Section 1: How hantavirus spreads

Infected deer mice shed the virus in their urine, droppings, and saliva. When fresh rodent urine, droppings, or nesting materials are stirred up (commonly through sweeping or vacuuming), tiny droplets containing the virus get into the air. People get hantavirus infection by breathing in air contaminated with the virus. Hantavirus infection in the US does not spread from person to person.

There are several other less common ways rodents may spread hantavirus to people:

  • If a rodent with the virus bites someone, the virus may be spread to that person, but this type of transmission is rare.
  • Researchers believe that people may be able to get the virus if they touch something that has been contaminated with rodent urine, droppings, or saliva, and then touch their nose or mouth.
  • Researchers also suspect people can become sick if they eat food contaminated by urine, droppings, or saliva from an infected rodent.
  • Opening and cleaning previously unused buildings where deer mice have been.
  • Housecleaning activities when you have a deer mouse infestation (sweeping/vacuuming can stir up dust) or other activities that stir up dust like moving boxes or other items in an area where deer mice have been.
  • Work-related exposure for those in construction, utility and pest control. These persons can be exposed when they work in crawl spaces, under houses, or in vacant buildings that may have a rodent population.
  • Camping and hiking. Campers and hikers can also be exposed when they use infested trail shelters or camp in other rodent habitats.
  • Exposure to deer mouse nesting materials or droppings in a car, including possibly through infestation in the passenger area or the car cabin air filter, duct work, and vents.

Ticks, fleas, mosquitoes, and other biting insects are not known to transmit hantavirus.

Hantaviruses that cause HPS in the United States are known to be transmitted only by certain species of rodents (deer mice in Washington.) Dogs and cats are not known to carry hantavirus; however, they may bring infected rodents into contact with people if they catch such animals and carry them home. Guinea pigs, hamsters, gerbils, and rodents from pet stores are not known to carry hantavirus. Cats and dogs may be infected through contact with deer mice, but they are not known to transmit the virus.

Section 2: Hantavirus and deer mice

Deer mice are generally not associated with urban environments. However, deer mice will enter human habitation seeking shelter and food in rural and suburban areas. People living in these areas have an increased risk compared to those living in the middle of the city.

The deer mouse is the major reservoir of the Sin Nombre hantavirus that causes human disease in the western United States. Deer mice live in all parts of Washington, but mainly in rural areas. The deer mouse is about six inches long from the nose to the tip of its tail. It is grayish to light brown on top, with a white belly, large ears and eyes, and a furry tail that is white on the underside. Deer mice usually carry the virus without showing any signs of being sick. The deer mouse and the house mouse are different species, and the house mouse does not carry hantavirus. In addition, rats also do not carry hantavirus in Washington state.

Types of mice

Refer to our Hantavirus information sheet on how to appropriately get rid of rodents from your homes and clean up droppings and urine from rodents in your home. For more detailed information, the CDC has a brochure.

Public Health should be consulted and special precautions are indicated for cleaning homes or buildings with:

  • heavy rodent infestations (piles of feces, numerous rodent nests or dead rodents)
  • vacant dwellings that have attracted rodents while unoccupied
  • dwellings and other structures that have been occupied by persons with confirmed hantavirus infection

Public Health recommends hiring professional pest control services in these situations. In general, we would not recommend treating a household as a biohazard site.

Rodent infestations in vehicles have been previously recognized as possible means of hantavirus exposures, and precautions should be taken to carefully clean the car if evidence of rodents is found. The same principles that are described for cleaning a home infested with rodents would apply to cleaning a vehicle infested with rodents. Refer to information about cleaning and disinfecting vehicles with rodent infestations.

How widespread hantavirus is within the deer mice population varies by time and location. On average, about 10% of deer mice tested in Washington state during 1993-2001 were positive for hantavirus. We are not aware of more recent studies of hantavirus and deer mice in our region.

We do not recommend testing deer mice for hantavirus because the results from mice that are trapped do not represent all mice in the home, and even if the test was negative we recommend the same precautions: If you have deer mice you should take precautions to seal up your home, trap mice, and clean up using appropriate precautions.

Section 3: If you think you've been exposed to hantavirus

Testing is not useful for persons who have been near rodents or had a rodent exposure but have not developed symptoms because blood tests cannot detect infection before symptoms appear. Even if symptoms develop, testing can be negative early in the illness and a negative test does not rule out hantavirus infection.

If you do have symptoms, seek healthcare and report your rodent exposure to your provider who will determine if testing is needed.

There is no specific drug to treat hantavirus infection, nor is there medication to prevent illness if you have been exposed. Treatment of patients with HPS with good supportive hospital care is important. Learn more from the CDC.

A blood test would not be able to pick up evidence of infection before symptoms appear. Tests for specific hantavirus antibodies are generally positive within a few days after onset of symptoms.

Symptoms begin 1-8 weeks after inhaling the virus. Illness typically starts with 3-5 days of symptoms including fever, sore muscles, headaches, and fatigue; nausea, vomiting, and diarrhea may be present. Four to 10 days later, the late symptoms of HPS appear. As the disease gets worse, it causes coughing, shortness of breath, and difficulty breathing.

If you live in or have been exposed to areas with deer mice or rodents and have symptoms of hantavirus, seek healthcare immediately and tell your provider about your exposure.