Hantavirus Pulmonary Syndrome (HPS)

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Hantavirus pulmonary syndrome (HPS) facts

  • Hantaviruses are RNA viruses that are transmitted to human by rodents.
  • Hantavirus pulmonary syndrome (HPS) is a disease in which in the late stage of infection with a hantavirus subtype, patients experience lung congestion, fluid accumulation in the lungs, and shortness of breath. Death occurs in about 38% of patients. Early symptoms (fatigue, fever, muscle aches) are nonspecific.
  • Hantavirus was first identified in an outbreak in 1993 in the "Four Corners" area of the southwestern U.S. and found to be transmitted to humans by rodent urine, feces, saliva, and by airborne particles containing these items. The 2012 outbreak at Yosemite National Park was due to hantavirus transfer to humans by deer mice. Human-to-human transmission of hantavirus in the Americas has not been documented.
  • HPS is caused by hantaviruses that cause lung capillaries to leak fluid into the lung tissue.
  • HPS is usually diagnosed presumptively by the patient's lung symptoms or the patient's association with rodents, or the patient's probable contact with rodent-contaminated airborne dust; chest X-rays provide additional evidence, but definitive diagnosis is usually done at a specialized lab or the CDC.
  • There is no specific treatment of HPS; patients are usually treated in an intensive-care facility and often require respiratory support (intubation and mechanical ventilation).
  • Risk factors are any association with rodents and their airborne body excretions.
  • Complications of HPS are death in about 38% of patients; if the HPS patient survives, there are usually no long-term complications.
  • For patients who survive HPS, the prognosis is very good without complications.
  • Prevention of HPS centers on avoidance of rodent contamination; there is no vaccine available to prevent hantavirus infection or HPS.
Picture of Sin Nombre hantavirus particles
Figure 1: Picture of Sin Nombre hantavirus particles; SOURCE: CDC/D. Loren Ketai, MD
Picture of areas of the body that are affected by stress
Figure 2: Chest X-ray of a patient with hantavirus pulmonary syndrome (HPS); SOURCE: CDC/Brian W.J. Mahy, PhD; Luanne H. Elliott, MS
Medically Reviewed by a Doctor on 10/21/2014

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Hantavirus in Yosemite

What can I do to protect myself while in Yosemite or other areas around the U.S. where this has been found?

The park is a natural environment that contains wild animals, including rodents. All visitors should be aware of safety information related to visiting Yosemite, ranging from river safety to bear awareness and hantavirus awareness.

We do suggest that you are mindful of the steps that can be taken to reduce exposure to hantavirus. These include:

  • Avoid touching live or dead rodents or disturbing rodent burrows, dens, or nests.
  • Keep food in tightly sealed containers (including those stored in bear boxes) and store away from rodents.
  • Take care not to stir up dust.
  • Minimize storage of luggage and other materials on floors.
  • Contact housekeeping or maintenance if signs of rodents are present, including feces or urine.
  • Do not pitch tents or place sleeping bags in proximity to rodent feces or burrows or near possible rodent habitat (for example, dense brush or woodpiles).
  • Avoid sleeping on bare ground. Use a cot with the sleeping surface at least 12 inches above the ground or use a tent with a floor.
  • Dispose of all trash and garbage promptly in accordance with campsite regulations by burning, discarding in rodent-proof trash containers, or packing it out in rodent-proof containers.
  • If visitors notice rodent droppings, they should contact staff immediately. National Park Service and concessioner staff are trained and equipped to respond to evidence of rodent activity.


National Park Service