Article

Hantavirus Pulmonary Syndrome

For information on other illnesses that can affect NPS employees, volunteers, commercial use providers, and visitors, please see the NPS A–Z Health Topics index.
deer mouse
Deer Mouse

NPS/John Good

Overview

Hantavirus Pulmonary Syndrome is a respiratory disease caused by a virus that is spread by some species of rodents. Hantavirus can lead to serious illness and is sometimes fatal.

The deer mouse is the primary host in western states. The white-footed mouse is the primary host in eastern states. Hantavirus cases occur sporadically and usually in rural areas where the rodent hosts live. Most cases of hantavirus in the United States occur in western states.

Hantaviruses are shed in the urine, feces, and saliva of infected rodents. The infectious particles can be transmitted to humans when they are inhaled, ingested, or when is a person is bitten by an infected rodent.

The type of hantavirus present in the United States cannot be transmitted from person to person. The time from the initial exposure to the appearance of symptoms can be 1–8 weeks. If you have been exposed to rodent droppings, it is important to monitor your health for symptoms up to 8 weeks after the exposure.

Early symptoms of HPS include: fatigue, fever, and muscle aches, and may also include headaches, dizziness, chills, nausea, vomiting, and diarrhea. Four (4) to 10 days after the initial phase, late symptoms of coughing and difficulty breathing appear. The mortality rate of HPS is 38%. If you experience these symptoms, please seek medical care. Tell your doctor you were exposed to rodents so they can take the proper steps.

Diagnosing hantavirus can be initially difficult because symptoms can be similar to other illnesses. Diagnosis should be based on both clinical signs, diagnostics, and a history of potential rodent exposure. There is no specific treatment or vaccine for hantavirus, so prevention of exposure to the virus is key.

Animals: As the vector of hantaviruses, rodents carry the virus but experience no or mild illness from the virus. There is some evidence that domestic animals including dogs and cats may become infected with hantaviruses, but they do not experience clinical illness and cannot transmit the virus to humans. Healthy ecosystems with natural predators and more types of rodent species have lower rates of hantavirus and are less risk to humans. Less diverse rodent communities with fewer predators, such as those found in disturbed and human-developed areas, have higher rates of hantavirus.

Environment: Disease surveillance shows that hantavirus occurs predominantly in the Western United States, and more specifically the four corners region including Arizona, Colorado, New Mexico, and Utah.

Rodents that transmit hantavirus may be found in certain settings including places where animal or human food and warm is found, such as barns, stables, and poorly sealed houses, garages, and shed. Most human cases of hantavirus occur in the spring and are associated with buildings that became heavily infested with rodents seeking winter shelter. Preventing rodents from entering human structures is the best way to eliminate the risk for hantavirus.

Visitor Safety Information

If you see rodent droppings or signs of rodents:

  • Do not sweep, vacuum, or dust rodent droppings or nesting materials. Prevent dust particles from being created.

  • Report signs of rodents to the lodging manager, park ranger or visitor center immediately.

If you become ill following a potential exposure to rodent droppings, take these steps:

  • Contact your healthcare provider with information such as the date you were near or in the area of rodent droppings, the location where you were staying in the national park, the national park name and state.

  • Please report any confirmed illnesses to the NPS Office of Health and Safety at publichealthprogram@nps.gov.

Preventing Hantavirus For Employees, Residents, and Partners

  • Do not sweep, vacuum or dust in areas where there is rodent activity (for example: droppings, urine, saliva, and nesting materials).

  • Open windows to ventilate rooms for at least 30 minutes prior to cleaning. Use caution and avoid generating dust when opening/cleaning buildings that have been closed for a period of time.

  • Use proper procedures to clean up rodent infestations, especially in indoor spaces.

    • For light infestations, follow NPS guidance for cleaning up a light infestation (see below).

    • For heavy infestations (large rodent concentrations and/or droppings), especially in enclosed, non-ventilated areas, consult public health and safety specialists before cleaning. These situations require more stringent personal protective measures and approved respirator fit testing within a respiratory protection program.

    • If you are unsure if an infestation is light or heavy, it is better to err on the side of caution

  • Seal up openings in buildings to prevent rodents from entering. Exclude rodents from living quarters as directed in the NPS Rodent Exclusion Manual 2017 and NPS Rodent Exclusion video and NPS Indoor Rodent Management for NPS Properties (internal access). Important actions to take to exclude rodents are:

    • Check buildings for gaps or holes greater than ¼ of an inch and seal them with rodent-proof material to prevent rodent entry.

    • Minimize food and water sources, as well as places that are convenient for rodents to build nests.

    • Minimize or eliminate vegetation, wood piles, and debris within 18 inches of building foundations.

  • Trap rodents in areas of concern.

    • Monitor for signs that rodents are present (including rodent droppings and gnaw marks) and take action immediately if you see signs.

    • Use multiple snap traps baited with fresh bait and checked daily to catch rodents. Use proper cleaning procedures to pick up and dispose of rodents and disinfect snap traps. See the Fact Sheet Below.

    • Place traps against the wall. Position the bait pan directly against the wall in places where rodent signs, such as droppings, have been seen.

    • Keep traps set to monitor for new rodent activity, particularly in the fall when rodents attempt to move indoors.

Directions for Cleaning a Light Infestation

The following instructions are for cleaning light infestations. Rodents may carry fleas. Use insect repellant (DEET or other EPA-registered repellants) on clothing, shoes, and gloves when picking up dead rodents and cleaning droppings and nesting materials to reduce the risk of flea bites and exposure to flea borne disease.

Heavy rodent infestations require more stringent personal protective measures and an approved respiratory program (RPP). Heavy infestations are generally considered to be an area of rodent droppings or nesting materials that is larger than a boot print. If you think you have a heavy infestation, reach out to your park safety office.

  1. Open windows to ventilate rooms for at least 30 minutes prior to cleaning. Leave the area during this period. Direct sunlight also helps to inactivate the virus. Take care not to stir up dust and NEVER sweep or vacuum.
  2. Dilute disinfectant to obtain either a 1:10 bleach solution or obtain an EPA registered disinfectant. Diluted solutions MUST be made fresh daily or it will be ineffective. If using a disinfectant, be sure the chosen product is labeled as a disinfectant and has an EPA registration number. If using on a surface, Consider how the product may affect the surface to be cleaned prior to use and do a patch test. NEVER mix bleach with a disinfectant solution. It will cause toxic fumes.
  3. Wear gloves when cleaning or disposing of traps. Re-usable gloves must be disinfected after use.
  4. Soak the droppings, nest, rodent, and/or trap thoroughly with disinfectant solution and spray at least a 2-foot area around the trap. Spray/soak any associated droppings and urine. Allow to sit undisturbed for at LEAST 10 minutes.
  5. Invert a plastic bag over the gloved hand, unfold it over the droppings, trap and rodent carcass as you pick them up. Tie-off or seal bag. Please sealed bag into another plastic bag and seal. Always keep the rodent at an arm’s length and take care not to stir up dust. NOTE: Traps can be re-used if they are disinfected or left in the sun for several hours. Rinse any disinfectant from the trap prior to reuse as the scent of disinfectants can deter future rodents. Leaving traps in sunlight for several hours will inactivate the virus and help dissipate disinfectant odors.
  6. Respray any exposed droppings with the disinfectant and then use a disposable paper towel to clean up any visible droppings.
  7. Spray gloves (while on hands). If the gloves are disposable, place in plastic bag, seal, and throw into the trash. If a respirator and goggles were worn, lay in direct daylight for at least an hour. Wash hands with soap and water after gloves are removed.
  8. Dispose of all bagged trash in a regularly emptied or collected receptacle in accordance with local trash policies.
  9. Steam clean upholstery, shampoo with a disinfectant, or dispose of heavily contaminated items. For difficult to clean materials such as books, papers, or museum specimens, place outdoors in sunlight for several hours or in an indoor area free of rodents for a minimum of three and up to six weeks. Consult the NPS Conserve-o-gram on Hantavirus Safety for more information.

Kit Components

  • Snap traps (10 for a normal sized room)

  • Hand sprayer (32 oz. Spritzer bottle or 2 gallon wand type sprayer)

  • Bleach or household disinfectant

  • Plastic bags, small and large

  • Gloves (double-layer rubber, latex or nitrile or reusable rubber, nitrile)

Trapping Tips:

  • Place bail pan with trigger end of trap directly against wall - leave no space

  • Place two trap side-by-side to increase effectiveness

  • Bait with a cotton ball if traps will be left for a longer period of time. Refresh perishable baits such as peanut butter often.

  • Leave snap traps set to monitor for rodent activity, especially during fall months as rodents attempt to find shelter indoors.

Contact Information

Visitors:

  • For questions regarding a health concern that may be related to your park visit, email us.
  • If you have any medical related questions, please contact your healthcare provider who will report any confirmed and reportable disease on your behalf to the local or state health department.

Concessioners & Partners:

Employees & Volunteers:

  • NPS staff and volunteers should contact their park safety office for guidance on a work-related disease exposure.
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Resources

NPS RESOURCES:

OTHER RESOURCES:

NPS-SPECIFIC PUBLICATIONS:

  • Danforth ME, Messenger S, Buttke D, et al. Long-Term Rodent Surveillance after Outbreak of Hantavirus Infection, Yosemite National Park, California, USA, 2012. Emerg Infect Dis. 2020;26(3):560-567. doi:10.3201/eid2603.191307

  • Pesapane R, Enge B, Roy A, et al. A Tale of Two Valleys: Disparity in Sin Nombre Virus Antibody Reactivity Between Neighboring Mojave Desert Communities. Vector Borne Zoonotic Dis. 2019;19(4):290-294. doi:10.1089/vbz.2018.2341

  • Burns JE, Metzger ME, Messenger S, et al. Novel Focus of Sin Nombre Virus in Peromyscus eremicus Mice, Death Valley National Park, California, USA. Emerg Infect Dis. 2018;24(6):1112-1115. doi:10.3201/eid2406.180089

  • Wilken JA, Jackson R, Materna BL, et al. Assessing prevention measures and Sin Nombre hantavirus seroprevalence among workers at Yosemite National Park. Am J Ind Med. 2015;58(6):658-667. doi:10.1002/ajim.22445

  • Núñez JJ, Fritz CL, Knust B, et al. Hantavirus infections among overnight visitors to Yosemite National Park, California, USA, 2012. Emerg Infect Dis. 2014;20(3):386-393. doi:10.3201/eid2003.131581

  • Hartline J, Mierek C, Knutson T, Kang C. Hantavirus infection in North America: a clinical review. Am J Emerg Med. 2013;31(6):978-982. doi:10.1016/j.ajem.2013.02.001

  • Outbreak news. Hantavirus pulmonary syndrome, Yosemite National Park, United States of America. Wkly Epidemiol Rec. 2012;87(37):345-346.

  • Hantavirus pulmonary syndrome in visitors to a national park--Yosemite Valley, California, 2012. MMWR Morb Mortal Wkly Rep. 2012;61(46):952.

  • Zeitz PS, Graber JM, Voorhees RA, et al. Assessment of occupational risk for hantavirus infection in Arizona and New Mexico. J Occup Environ Med. 1997;39(5):463-467. doi:10.1097/00043764-199705000-00013

  • Glass GE, Johnson JS, Hodenbach GA, et al. Experimental evaluation of rodent exclusion methods to reduce hantavirus transmission to humans in rural housing. Am J Trop Med Hyg. 1997;56(4):359-364. doi:10.4269/ajtmh.1997.56.359

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Last updated: July 24, 2025