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Hantavirus Pulmonary Syndrome

(This page is part of a series. 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

Humans: Hantavirus Pulmonary Syndrome is respiratory disease caused by a virus transmitted by some species of rodents. Hanta virus can lead to serious illness and is sometimes fatal. Cases occur sporadically and are usually associated with heavily infested buildings in rural areas where the rodent hosts live In the Western United States. The deer mouse is the primary host and in the Eastern part of the country, the white-footed mouse is the primary host.

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.

Hanta viruses 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, with most cases developing symptoms within 3 weeks of exposure.

Early symptoms of HPS include fatigue, fever, and muscle aches, and may also include headaches, dizziness, chills, nausea, vomiting, and diarrhea. Four to 10 days after the initial phase, late symptoms of coughing and difficulty breathing appear. The mortality rate of HPS is 38%.

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.

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.

ACTIONS TO TAKE
If you see rodent droppings or signs of rodents:
  • Do not not disturb the droppings. Avoid activities like sweeping or dusting to prevent dust particles.
  • 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 HANTA VIRUS EXPOSURE FOR EMPLOYEES

  • Avoid contact with rodents their droppings, urine, saliva, and nesting materials.
  • Open windows to ventilate rooms for at least 30 minutes prior to cleaning. Use caution when opening/cleaning buildings that have been closed for a period of time.
  • 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. Keep traps set to monitor for new rodent activity, particularly in the fall when rodents attempt to move indoors, placing the bait pan directly against the wall in places where rodent signs such as droppings have been seen.
  • 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

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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

Last updated: June 25, 2025