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

NPS/John Good

THE BASICS
Humans: Hantavirus Pulmonary Syndrome is a sometimes fatal, respiratory disease caused by a virus transmitted by some species of rodents. 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 thus less risk to humans, while less diverse rodent communities with fewer predators, such as those found in disturbed and human-developed areas, have higher rates of hantavirus. Hantaviruses are shed in the urine, feces, and saliva of infected rodents. The infectious particles are inhaled, ingested, or transmitted through a bite to a susceptible person. 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.

PREVENTION

• Avoid contact with rodents their droppings, urine, saliva, and nesting materials.
• Take care when opening/cleaning buildings that have been closed for a period of time. Open windows to ventilate rooms for at least 30 minutes prior to cleaning.
• Seal up. 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). Some key recommendations include:
  • 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 up. 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.
• Cleanup. 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

RESPONSE

• Information about rodents inside buildings should be reported to park maintenance staff or a supervisor immediately.
• If you become ill following a potential exposure, contact your healthcare provider and let them know of your concern. Also, please report any confirmed illnesses to the NPS Office of Public Health [e-mail] as directed in the “Disease Reporting” guidance below.
• Report concerns about sick or dead wildlife to the park resource manager and the Wildlife Health Branch at e-mail us

Last updated 5/23/2023

Directions for Cleaning a Light Infestation

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 vacuum.

2. Dilute disinfectant to obtain either a 1:10 bleach solution or obtain an EPA registered disinfectant. Diluted bleach MUST be made fresh daily or it will be ineffective. Be sure chosen product is labeled as a disinfectant, has an EPA registration number, and consider how the product may affect the surface to be cleaned prior to use.

3. Make sure gloves are worn when tending traps or sites. Re-usable gloves must be disinfected after use.

4. Leave in place and 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 if using dilute bleach or follow the label directions for other disinfectants.

5. Invert a plastic bag over the gloved hand, unfold it over the droppings and/or trap and rodent carcass as you pick up the trap and rodent carcass and tie-off or seal bag. Seal and place bag into another plastic bag and seal, always keep rodent at an arm’s length and take care not to stir up dust. Traps can be re-used if they are disinfected and the disinfectant is rinsed 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) and, if disposable, place in plastic bag, seal, and dispose. If a respirator and goggles were worn, lay in direct daylight for at least an hour. Wash hands with soap and water.

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.

If you are uncertain of whether the infestation is light or heavy, consult with your safety manager or wear a respirator and googles if you have been medically cleared and fit-tested for wear.

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 (doubled-up rubber, latex or nitrile or reusable rubber, nitrile)

 

NPS RESOURCES:

• NPS Hantavirus Fact Sheet and Clean/Trapping Instructions (combined)
• NPS IPM Indoor Rodent Management for NPS Properties (restricted access)
• NPS Rodent Exclusion Manual (2014)
• NPS Rodent Exclusion Video (2017) (restricted access)
• NPS Proper Use and Placement of Snap Traps
• NPS Integrated Pest Management: Rodent Management (restricted access)
• Pest and Invasive Species Management: Hantavirus (restricted access)
• NPS Conservogram (available upon request to [e-mail])

OTHER RESOURCES:

• CDC Hantavirus webpage
• CDC “How to Control Wild Rodent Infestations” webpage
• CDC “You Can Prevent Hantavirus” brochure

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

Disease Reporting

Visitors: Please email us to report any disease or health concern you believe may be related to your visit. You should also contact your healthcare provider who will report any confirmed and reportable disease on your behalf to the local or state health department.

Concessioners & Partners: Please email us to report illnesses as defined in NPS guidance and policy and in the Concessions contract.

Employees & Volunteers: NPS staff should report all employee and volunteer incidents as defined in NPS guidance and policy by contacting your NPS Public Health Consultant (restricted access), or you can email us. All work-related exposures and illnesses must also be reported in the Safety Management Information System (SMIS) (restricted access). All known disease exposures should be reported in SMIS as well.