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FAQs Reqarding Hantavirus Infection in Yosemite National Park for U.S. Visitors to Yosemite

Updated: September 17, 2012

The questions and answers below provide information for recent U.S. visitors to Yosemite and health care providers regarding the risk of exposure, diagnosis and testing for Hantavirus Pulmonary Syndrome (HPS) among recent visitors to Yosemite National Park, as well as links and phone numbers for further information.

I'm from the U.S. and stayed in Yosemite National Park recently. Should I seek medical attention?

If you exhibit any symptoms of HPS, seek medical attention immediately.

Early HPS symptoms include fatigue, fever and muscle aches, especially in the large muscle groups—thighs, hips, back, and sometimes shoulders. These symptoms occur in all instances of HPS infection. There may also be headaches, dizziness, chills, and abdominal problems, such as nausea, vomiting, diarrhea, and abdominal pain. About half of all HPS patients experience these symptoms.

Four to 10 days after the initial phase of illness, the late symptoms of HPS may appear. These include coughing and shortness of breath, with the sensation, as one former HPS patient put it, of a "tight band around my chest and a pillow over my face," as the lungs fill with fluid.

If you subsequently develop respiratory difficulties or shortness of breath, you should immediately seek medical attention.

CDC-INFO on hantavirus/HPS:
(800) CDC-INFO
CDC Hantavirus Hotline:
(877) 232-3322 or (404) 639-1510

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I was hiking in Yosemite for just one day in July. During my hike, I didn't see or touch any rodents. Am I at risk for developing Hantavirus Pulmonary Syndrome?

The risk of contracting HPS while hiking is extremely low. HPS is a very rare disease. In the U.S., the type of hantavirus that causes HPS is known as Sin Nombre Hantavirus. The host of the Sin Nombre hantavirus is the deer mouse (Peromyscus maniculatus), which is present throughout the western and central U.S., including Yosemite National Park. It is important to note that approximately 12 percent of deer mice carry the virus. Also, after the virus is excreted in the deer mouse’s urine or feces, it quickly becomes inactivated and non-infectious.

So, if you were hiking in Yosemite for the day and did not touch or see any rodents, there is very little risk for HPS.

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I visited Yosemite National Park recently. I now have a headache, have vomited, and have diarrhea. What should I do?

Early HPS symptoms include fatigue, fever and muscle aches, especially in the large muscle groups—thighs, hips, back, and sometimes shoulders. These symptoms occur in all instances of HPS infection. There may also be headaches, dizziness, chills, and abdominal problems, such as nausea, vomiting, diarrhea, and abdominal pain. About half of all HPS patients experience these symptoms.

Therefore, you should contact your health provider to determine if testing for HPS is needed. If you subsequently develop respiratory difficulties or shortness of breath, you should seek immediate medical care.

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I had lunch in Curry Village in Yosemite, but I did not stay there. Am I at risk for developing HPS?

HPS is a very rare disease. In the U.S., the type of hantavirus that causes HPS is known as Sin Nombre Hantavirus. The primary host of the Sin Nombre hantavirus is the deer mouse (Peromyscus maniculatus), which is present throughout the western and central U.S., including Yosemite National Park. It is important to note that not that fewer than 20 percent of deer mice carry the virus. Also, after the virus is excreted in the deer mouse's urine or feces, it quickly becomes inactivated and non-infectious.

So, if you visited Yosemite but did not stay there for long, and you didn't touch or see any rodents, there is very little risk for HPS.

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When I was in Yosemite National Park recently, I saw a mouse in my tent. Should I seek medical attention?

Not unless symptoms appear. Early HPS symptoms include fatigue, fever and muscle aches, especially in the large muscle groups—thighs, hips, back, and sometimes shoulders. These symptoms occur in all instances of HPS infection. There may also be headaches, dizziness, chills, and abdominal problems, such as nausea, vomiting, diarrhea, and abdominal pain. About half of all HPS patients experience these symptoms.

Four to 10 days after the initial phase of illness, the late symptoms of HPS may appear. These include coughing and shortness of breath, with the sensation, as one former HPS patient put it, of a "tight band around my chest and a pillow over my face," as the lungs fill with fluid.

If you subsequently develop respiratory difficulties or shortness of breath, you should immediately seek medical attention.

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I visited Yosemite National Park in May of 2012. After returning home, I felt sick, with symptoms that resemble HPS. I'm well now. What should I do?

Contact your doctor or your state epidemiologist. Mention your symptoms and your travel to Yosemite. They will decide if a laboratory test is needed to determine whether you had HPS.

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I stayed in Yosemite National Park in the summer of 2011, over a year ago. Am I at risk for HPS?

No. Symptoms of the disease may occur anywhere from 1-6 weeks after exposure to the virus. Typically, it's 2-4 weeks. So, since it was over a year ago, there's no reason to believe you're at risk for HPS.

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Is there a test for HPS?

Yes. Testing for HPS is possible in a specialized laboratory. Only a laboratory test can confirm if you have or had HPS. Diagnosing clinical HPS in an individual who has been infected for only a few days is difficult, because early symptoms such as fever, muscle aches, and fatigue are easily confused with other illnesses.

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If my doctor thinks I may have HPS, how can I get tested?

Some state health departments maintain laboratories that can test for HPS. State health departments that cannot test for HPS can send blood samples to CDC for diagnostic testing, but only after prior consultation with CDC. Because HPS is a nationally notifiable disease, your doctor should contact your state health department to report suspected cases and follow their guidance on submission of samples for HPS testing.

State-specific information on submission of samples for testing

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How is HPS treated? Is there a vaccine for HPS?

There is no specific treatment, cure, or vaccine for HPS. However, if infected individuals are recognized early and receive medical care in an intensive care unit, they may do better. In intensive care, patients are given oxygen therapy or undergo an intubation procedure (insertion of a flexible tube in the airway) to help them through the period of severe respiratory distress.

If you have been around rodents and have symptoms of fever, deep muscle aches, and severe shortness of breath, see your doctor immediately. Be sure to tell your doctor that you have been around rodents.

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I was in Yosemite National Park in May 2012, staying at the "Signature Tent Cabins" in Curry Village. I am feeling fine. Is there still a chance that I could become sick with Hantavirus Pulmonary Syndrome?

No. Because the incubation of hantavirus is between one and six weeks, and because your stay in May puts you 'outside' that incubation period, you are not at risk for developing Hantavirus Pulmonary Syndrome related to your stay in Curry Village.

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I was in Yosemite National Park on August 16, 2012. I never had any symptoms after returning home. Should I be tested, just to be sure that I am not infected?

People without any symptoms should not be tested. However, the incubation period of the virus is from one to six weeks. You should monitor your health until the end of September, six weeks after your visit in mid-August.

For persons who do not have any symptoms of Hantavirus Pulmonary Syndrome, testing does not yield meaningful results. For testing to be definitive, symptoms should be present for 3-4 days, in order to measure your immune system's response to the virus.

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Do I have to have all the symptoms listed on the CDC webpage in order to have Hantavirus Pulmonary Syndrome?

No. However, some symptoms, or groups of symptoms, are more indicative than others. If you are feeling sick with a high fever and develop any difficulty breathing, seek medical attention immediately. If you had any recent potential exposure to deer mice (including camping in Yosemite), tell your healthcare provider about it and mention hantavirus.

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My girlfriend/boyfriend was hiking and camping in Yosemite in August 2012. Can I become infected through contact with her/him?

No. There is no documented human-to-human transmission of hantavirus in the US.

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  • Page last reviewed: September 17, 2012
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