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Yosemite Deaths Raise Questions About Hantavirus Pulmonary Syndrome
By Daniel J. DeNoon
Reviewed by Louise Chang, MD
Aug. 29, 2012 -- Two of four people have died after getting hantavirus infection at Yosemite National Park.
About 1,700 people who visited the park from mid-June to mid-August 2012 received scary emails or letters from the National Park Service. The emails and letters warn park visitors they may have been exposed to mice carrying hantavirus -- and to look out for signs that they might have deadly hantavirus disease.
That disease -- hantavirus pulmonary syndrome or HPS -- kills nearly 40% of people who get it.
What is hantavirus?
In the early 1990s, there was an outbreak of a mysterious and deadly disease in the Four Corners area of Arizona, Colorado, New Mexico, and Utah. An equally mysterious virus, dubbed Sin Nombre virus, caused the illness.
Sin Nombre virus turned out to be a member of the hantavirus family. Although other hantaviruses can cause fatal illness, none is as deadly as the Sin Nombre virus. It causes a disease called hantavirus pulmonary syndrome (HPS).
Other strains of hantavirus also cause HPS in the U.S. These include New York hantavirus in Northeastern states, and Black Creek Canal hantavirus and Bayou hantavirus in Southeastern states. By the end of 2011, 34 states reported HPS cases. The vast majority were in Western and Southwestern states.
How do people get hantavirus infection?
Mice and rats spread hantaviruses among themselves. The droppings, urine, saliva, and blood of infected animals are chock-full of virus particles.
Deer mice carry the Sin Nombre strain of hantavirus. Cotton rats and rice rats carry hantavirus in the Southeast, while white-footed mice carry hantavirus in the Northeast.
Although it's possible to get hantavirus infection from a mouse or rat bite, such infections are rare. Most people get it by inhaling dust contaminated by rodent droppings or by touching rodent urine and then touching their mouth, eyes, or nose.
Getting infected is easier than it might seem. For example, you might go into your garage and scare off some mice nesting in an old cardboard box. The frightened mice leave behind a trail of urine. You pick up the mess they've left behind. You sweep up the droppings. The air fills with dust, which you breathe into your lungs.
Even healthy people who inhale hantavirus can get a fatal infection.
Hantavirus cannot spread from person to person. Contact with rodents is the only known risk.
What are the symptoms of hantavirus pulmonary syndrome (HPS)?
The hantavirus incubation period -- the time between infection and first symptoms -- isn't known for sure. The CDC notes that HPS symptoms tend to appear one to five weeks after exposure to rodent droppings, urine, or saliva.
It's hard to tell these early symptoms from symptoms of the flu or other common illnesses. But if you get these symptoms one to six weeks after contact with rodents or their droppings, tell your health care professional immediately.
Late symptoms begin to appear four to 10 days after the early symptoms. These include coughing and shortness of breath. It becomes harder and harder to breathe. All patients must be hospitalized and nearly all need mechanical ventilators to survive.
The disease is often fatal, with an overall mortality rate of 36% in the U.S. In 2011, there were 24 cases with 12 deaths.
What is the treatment for hantavirus infection?
There's no specific treatment for hantavirus infection. Known antiviral drugs do not help. There is no vaccine.
The sooner people with hantavirus infection get intensive care, the better their chances of survival. Those who get care only when they can barely breathe do worst.
If you've had a rodent exposure and get any of the early symptoms, contact your health care professional immediately.
How can I protect myself against hantavirus infection?
Rodent infestations are extremely common. Keeping rodents out of your house and out of your campsite is important. Some tips:
Despite our best efforts, rodents sometimes get into our houses and storage areas.
Before cleaning up, trap the rodents and seal the holes where they got in. Put on rubber, latex, or vinyl gloves and spray dead rodents with disinfectant or bleach solution. Let the disinfectant soak in for five minutes, then wrap the dead rodent in a paper towel or rag and put it in a plastic bag. Seal tightly, put in a second bag and seal it, then throw the bag in a covered trashcan.
When the traps have been untouched for a week, it's time to clean up.
The CDC suggests that after a week, virus in the rodent droppings, urine, and nesting materials should no longer be infectious. But don't take that for granted.
When cleaning up after a rodent infestation, the most important thing is NOT to create dust. DO NOT sweep or vacuum up rodent droppings.
Follow these steps:
SOURCES: CDC web site. Scott Gediman, assistant superintendent for public and legislative affairs, Yosemite National Park, California.