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Conservation > Fish & Wildlife Diseases Hantavirus

For questions/concerns about this disease in humans, please call your doctor or the Montana Department of Public Health and Human Services  (DPHHS).


For questions about this disease/parasite in wildlife, please call the FWP Wildlife Health Lab at 406-577-7882.


Hantavirus Pulmonary Syndrome, or HPS, is a severe respiratory illness in humans that is caused by a virus of the Bunyaviradae family. The virus is carried by rodents, and can be present in their urine, saliva, and droppings. Hantavirus disease surveillance in humans in the United States began in 1993 during an outbreak of severe respiratory illness in the Four Corners region – the area where Arizona, Colorado, New Mexico, and Utah meet (CDC).  As of the end of 2019816 cases of hantavirus disease were reported in the United States since surveillance began in 1993 (CDC).


Hantavirus occurs naturally throughout most of North and South America (Western, 2009). Although most cases in the United States have occurred west of the Mississippi River, sporadic (single) cases have been reported in several eastern states. A map of human cases in the United States can be found on the CDC website From 1993-2021, there were 47 human cases of Hantavirus Pulmonary Syndrome in Montana, of which 11 were fatal.  Further information and a map of human cases in Montana by county can be found on the Montana DPHHS website.

Species affected

Infected wild rodents do not show signs of illness, but shed the virus into the environment in their feces, urine and saliva (CFSPH).

The deer mouse is the primary reservoir for hantavirus in Montana and most of the United States and Canada. However, other rodents can also serve as a source of infection. In the southeastern United States, cotton rats and rice rats also serve as reservoirs while the white-footed mouse serves as a reservoir throughout southern New England and the Mid-Atlantic and southern states, the midwestern and western states, and Mexico (CDC). Domestic pets are not believed to be a source of infection (Miller et al, 2003).


In the United States, deer mice (along with cotton rats and rice rats in the southeastern states and the white-footed mouse in the Northeast) are reservoirs of the hantaviruses. The rodents shed the virus in their urine, droppings, and saliva. The virus is mainly transmitted to people when they breathe in air contaminated with the virus (CDC).

When fresh rodent urine, droppings, or nesting materials are stirred up, tiny droplets containing the virus get into the air. This process is known as “airborne transmission“ (CDC).

There are several other 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.
  • Scientists 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.
  • Scientists also suspect people can become sick if they eat food contaminated by urine, droppings, or saliva from an infected rodent.

The hantaviruses that cause human illness in the United States cannot be transmitted from one person to another. For example, you cannot get these viruses from touching or kissing a person who has HPS or from a health care worker who has treated someone with the disease (CDC).

In Chile and Argentina, rare cases of person-to-person transmission have occurred among close contacts of a person who was ill with a type of hantavirus called Andes virus (CDC).

The length of time hantaviruses can remain infectious in the environment is variable and depends on environmental conditions such as temperature and humidity, whether the virus is indoors or exposed to the sun, and even on the mouse’s diet (which would affect the chemistry of its urine) (Western, 2009), but the virus may remain infectious for at least several days at room temperature.


Infected wild rodents do not show signs of illness, but shed the virus into the environment in their feces, urine and saliva (CFSPH).

Due to the small number of HPS cases in humans, the incubation time is not positively known. However, based on limited information, it appears that symptoms may develop between 1 and 8 weeks after exposure to fresh urine, droppings, or saliva of infected rodents (CDC).

Early symptoms include fatigue, fever, and muscle aches, especially in the large muscle groups—thighs, hips, back, and sometimes shoulders. There may also be headaches, dizziness, chills, and abdominal problems, such as nausea, vomiting, diarrhea, and abdominal pain (CDC).

Four to 10 days after the initial phase of illness, the late symptoms of HPS appear. These include coughing, difficulty breathing, low blood pressure and irregular heart rate. The mortality rate for HPS is about 38% (CDC).


 In North America, about 1 out of 3 people with HPS have died (Miller et al, 2003; Western, 2009).

Public Health Concerns

Official recommendations for prevention of HPS in humans can be found on the CDC website:

Hantavirus is a potentially fatal zoonosis and precautions should be taken to prevent infections. Control mice inside and outside and try to keep rodents out of your home and workplace. Seal up cracks and gaps in buildings that are larger than 1/4 inch, including window and door sills, under sinks around the pipes, in foundations and attics, and any rodent entry hole. Trap indoor rats and mice with snap traps, and always wear disposable gloves and wash hands with warm soapy water when handling trapped rodents. Remove rodent food sources and keep food (including pet food) in rodent proof containers.

Always take precautions when cleaning, sealing, and trapping rodent-infested areas. Wear disposable gloves, and always be careful not to stir up dust by vacuuming, sweeping, or any other means. Soak contaminated areas such as trapped mice, droppings, and nests with a 10% hypochlorite (bleach) solution. Mix 1½ cups of household bleach in 1 gallon of water (or 1 part bleach to 9 parts water). Once everything has soaked for 10 minutes, remove all the nest material, mice or droppings with a damp disposable towel, then mop or sponge the area with bleach solution. Steam clean or shampoo upholstered furniture and carpets with evidence of rodent exposure. Spray dead rodents with disinfectant and then double bag them along with all cleaning materials. Bury, burn, or throw out rodents in appropriate waste disposal system. Disinfect gloves with disinfectant or soap and water before taking them off. After taking off the clean gloves, thoroughly wash hands with soap and water (or use a waterless alcohol-based hand rub when soap is not available) (Western, 2009).


Centers for Disease Control and Prevention (CDC). Website. Accessed 1/18/2022

Center for Food Security and Public Health. (CFSPH). Website.

Miller, M.J.R., R.D. Dawson, and H. Schwantje. 2003. Manual of Common Diseases and Parasites of Wildlife in Northern British Columbia. University of Northern British Columbia.

Montana Department of Public Health and Human Services Website.

Western Wildlife Disease Workshop Notebook. 2009. Southeastern Cooperative Wildlife Disease Study. College of Veterinary Medicine, University of Georgia.