Dr. Paul Auerbach is the world's leading outdoor health expert. His blog offers tips on outdoor safety and advice on how to handle wilderness emergencies.See all posts »
Hantavirus in Yosemite National Park
Our National Parks are a treasured heritage, and one of the ways in which we appreciate the outdoors. Millions of visitors flock to the parks in order to camp, hike, climb, swim and most of all, appreciate the wonder and natural beauty of America. As with any other outdoor setting, there are risks of injuries and illnesses. A recent cluster of cases of hantavirus pulmonary syndrome apparently originating from Curry Village in Yosemite National Park this summer points this out.
Hantaviruses (such as the sin nombre virus) cause a syndrome characterized by a combination of fever, lung failure, kidney failure, shock, and bleeding. The viruses are spread in the excreta of rodents; in the United States, hantavirus pulmonary syndrome (HPS) has been linked to the deer mouse (Peromyscus maniculatus) and white-footed mouse (P. leucopus), as well as to the cotton rat (Sigmodon hispidus) and rice rat (Oryzomys palustris). The animals shed the virus in saliva, urine, and feces. Aerosols are the most likely route of transmission from rodents to humans. Insect bites have not yet been implicated in transmission. The virus found in the U.S. is not known to cause human-to-human transmission.
The deer mouse is a creature that is adept at squeezing through very small openings. In the case of Curry Village at Yosemite, mouse nests have been found in the wall spaces of tent cabins, and mice have tested positive for the virus from around the park.
HPS has been reported in most states west of the Mississippi River, as well as in a few eastern states. In Louisiana and Florida, two hantavirus species, bayou virus and Black Creek virus, have been identified. A person infected by the virus has an incubation period of 1 to 6 weeks after exposure, and then suffers from fever, muscle aches, headache, cough, dizziness, abdominal pain, nausea and vomiting, and diarrhea for a few days; this is followed by difficulty breathing, mottled skin on the limbs, shock, and, sometimes, bleeding. In the U.S., approximately a third of victims die.
Most victims have had an interaction with rodents, such as when cleaning a barn or capturing the animals. Unfortunately, there is not yet any specific therapy beyond supportive care. Because a person with hantavirus infection may become seriously ill at a rapid rate, it is important to promptly bring any suspected victim to medical care.
To avoid unnecessary exposure to hantavirus, it is recommended that wilderness enthusiasts observe the following precautions:
- keep food and water covered and stored in rodent-proof containers
- dispose of food clutter
- spray dead rodents, nests, and droppings with disinfectant before handling (wear gloves)
- clean and disinfect cabins and other shelters thoroughly before using
- don’t make camp near rodent sites
- don’t sleep on bare ground
- burn or bury garbage promptly
- discard food that looks like it may have been chewed upon by rodents
- use only bottled or disinfected water for campsite purposes.
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