Protecting Yourself From Hantavirus -- Experts Say Humans Are Most Likely To Contract This Disease When Sweeping Up A Shed, Garage Or Other Enclosed Space After A Deer-Mouse Infestation

When Seattleites Ross and Lisa Macfarlane first began going to their mountain cabin, "It was a housecat's dream," recalls Lisa ruefully. "There would be mouse droppings everywhere; little stashes of food under pillows and in boots, nesting material in the loft, the occasional decomposing body.

"We trapped ferociously, but we were pretty casual about the mouse poop. I know more than once, coming in late, I brushed droppings off the children's beds and plopped the kids down in them. After all, it was only mice."

Those casual days are over, alas. "What do we do now?" asks Lisa. "Wear those suits from `The Andromeda Strain'?"

Not quite. But if you've kept up with current events you may have learned that ordinary mice are being blamed for the spread of a deadly virus that has claimed the lives of some 70 people in less than three years.

The mouse in question is the deer mouse, Peromyscus maniculatus, the most common rodent in North America. The virus is a strain of hantavirus, one of a group known to infect a variety of rodents.

The deer mice themselves are totally unaffected by the virus.

(Had you conjured up a mental image of a crazed mouse, foaming at the mouth, lurching toward you? Sorry. Infected mice will skitter away from you just as fast as uninfected mice will.)

Research suggests 5 percent to 15 percent of deer mice in the Northwest carry hantavirus. In the Southwest, where hantavirus disease in humans was first found, an estimated 30 percent of deer mice are virus carriers.

These mice shed the virus in their feces, urine and saliva. Humans catch it by inhaling airborne particles of those materials. According to investigators, this is most likely to happen when sweeping up a shed, garage or other enclosed space after a mouse infestation. Pets, livestock and other animals do not get hantavirus. And humans cannot catch it from one another.

Researchers don't know yet how long hantavirus can live outside its host. Some viruses die very quickly. Others, such as smallpox and hepatitis A, are very tenacious. Research suggests that the hantavirus can survive at least a few days in fecal matter. As one expert pointed out, though, it's really a moot point. Since you rarely know how old mouse droppings are, you're obliged to treat any with caution.

According to Dr. Jeffrey Duchin, an investigator on the original hantavirus outbreak for the Centers for Disease Control and Prevention and now working with the University of Washington and Seattle/King County Health Department, once you've caught the virus, it can take anywhere from two days to six weeks to develop symptoms.

In the early phase of hantavirus infection, the symptoms are flu-like: fever, muscle ache, headache, sometimes a cough, sometimes abdominal pain. This early phase lasts for several days to a week. Then the virus attacks the cardiopulmonary system, causing a bad cough, shortness of breath, and eventually severe pulmonary edema - fluid in the lungs.

Patients are treated with oxygen, blood-pressure regulators, IV fluids and, in most cases, mechanical ventilation, Duchin says.

So far, about 50 percent of hantavirus patients have died.

Very grim stuff. But don't order that "Andromeda Strain" suit just yet. First, what are your chances of catching hantavirus? In Washington state, they are still very low - almost one in a million. However, depending on where you live and what activities you undertake, your risk can be much higher - or lower.

According to Dr. John Grendan, epidemiologist and veterinarian with the Washington State Department of Health, the deer mouse is a country mouse, far more common in rural areas and, in this state, east of the Cascades. But it can also be found in suburbs and even in woodsier parts of cities. And a Snohomish County woman, and a Gulf Islands, B.C., man - living conspicuously west of the Cascades - have died of hantavirus infection this spring.

Still, the most common species seen locally is the common house mouse. It's the same size as a deer mouse - about 6 inches long from nose to tip of tail - but it lacks the deer mouse's distinctive white belly.

The people who develop hantavirus catch it at home, for the most part, or around the house - what scientists call peri-domestically. So what are high-risk activities where hantavirus is concerned? Cleaning up in enclosed buildings such as sheds, garages and seasonal dwellings where mice have been living.

Field biologists and rodent-control workers - people who log thousands of contacts with deer mice - don't catch hantavirus, probably because their work is out of doors. Nor do the traditionally vulnerable: the very young, the very old, the chronically ill. Instead, hantavirus has struck previously healthy young adults and the middle-aged, almost exclusively. Why?

Scientists speculate that it's because these are the people who clean up after an infestation of mice, raising a cloud of contaminated material, getting a face full of it and contracting hantavirus disease.

Obviously, to significantly lower your risk of contracting hantavirus, you should move to the center of a big city and never offer to clean up a shed. Failing that, health experts recommend the following measures:

Cleanup

If you are planning to open up a seasonal dwelling such as a beach house or mountain cabin, or any building you have reason to suspect might be infested with deer mice, you'll need inexpensive dust masks (the kind you buy at the hardware store), one or more plastic spray bottles filled with a one-part bleach to 10-parts water solution, or spray cans of commercial disinfectant. You'll also need rubber gloves, sponges and mops.

First air out the building for at least half an hour, and don't go back in until the mice have had a chance to escape and the dust has had a chance to settle.

Now go in. Is there any evidence of mice? If there is, do not sweep or vacuum. Put on gloves, spray all surfaces with your disinfectant, then wipe with a sponge or mop. You can spray the floor, allow it to dry and then sweep up or vacuum. Steam-clean rugs, carpets and upholstered furniture. Wash clothes and bedding in hot water, dry on high setting. If you find a dead mouse, spray it, too, then double-bag it, seal the bags and dispose of it in the trash. (Having fun yet?)

Keep them out

Mice can worm their way through openings the size of a dime, so mouse-proofing a house is not easy. Find every tiny little outlet to the outside and plug it with wads of steel wool. Remember to check around plumbing holes. Set snap traps in likely places and bait them with the trapper's bait of choice - peanut butter. It's aromatic, tasty and impossible to make a quick get-away with.

Disinfect traps before reusing.

And make sure your house doesn't attract mice in the first place.

Keep food in sealed containers. Be meticulous about sanitation.

Try not to let children wander about the house with food. Don't leave pet food dishes out overnight.

Eliminate possible nesting sites around the building: junked cars, old tires, trash piles. Granden has found deer-mouse nests in the dashboard of a junker and in a rusting barbecue.

When camping, keep away from anything that looks like rodent activity. Keep your food in sealed containers and out of the reach of animals. Don't pitch your tent near woodpiles, favored nesting places of deer mice.

For more information, contact your local health department.

Susan McGrath's column runs every two weeks in the Home/Real Estate section.

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VIRUS FIRST TRACED TO CONTACT WITH MICE DURING KOREAN WAR.

Hantavirus first surfaced as a public health threat in the 1950s, during the Korean War. Droves of GI's stationed in the Hantaan region of Korea developed a deadly hemorrhagic fever and kidney problems. Many died.

The virus was traced to contact with field mice. Today, about 100,000 people in Asia are known to develop hemorrhagic fever annually from the hantavirus, and some 15,000 of them die.

Here in North America, several strains of hantavirus are known to occur, each strain infecting a different rodent - in particular deer mice, cotton rats and Norway rats. None of these strains is known to infect humans.

Then, in 1993, a peculiar cluster of cases of severe respiratory disease in the Southwest set public-health authorities' antennae aquiver. The cases were peculiar because almost all involved previously healthy young adults. Nineteen developed the disease; 17 died.

Investigators from the U.S. Centers for Disease Control and Prevention traced the outbreak to a hantavirus, and the hantavirus to the deer mouse, the most common rodent in North America. An unusually wet spring had resulted in a deer-mouse population boom. Victims caught the virus from the mouse by inhaling airborne particles or droplets of its feces, urine and saliva.

To date, about 140 people in the United States and Canada have caught hantavirus disease; half have died.

As in the case of the original Hantaan virus, viruses are generally named for a geographical feature near their place of discovery. No one wanted this virus named for his area. So it has ended up with a rather poetic name: Sin Nombre, Spanish for without name.

Though the Sin Nombre virus was only identified in 1994, its deadly effects are not news to the Navaho. Navaho legend has it that if deer mice enter the hogan and infest clothing or bedding, those items must be burned or the young adults of the hogan will die.