Deadly Dust : No Reason to Panic, Scientists Say After Discovery of Hantavirus in Mice

After finding deadly hantavirus for the first time in Ventura County in two deer mice trapped near Wood Ranch, scientists on Wednesday said this: Don’t panic.

But don’t do anything risky either, they warned, such as cleaning up after a mouse infestation without proper safeguards.

People who inhale dust containing the dried urine or droppings of deer mice risk catching hantavirus.

Those infected by hantavirus suffer quickly worsening flu-like symptoms, such as chills, muscle ache, nausea, vomiting and shortness of breath.

Treated soon enough with oxygen and antiviral drugs, victims can survive.

Yet more than half of those who catch hantavirus die as their lungs fill up with fluid.

While hantavirus is not contagious from person to person, there is no known cure.

“There isn’t any reason to panic,” said Dick Davis, a biologist with the California Department of Health. “It’s just a matter of using good sense and some degree of caution,” such as wearing a dust mask, rubber gloves and using disinfectant when cleaning up after mice.

“Hantavirus,” he added, “has probably been around for a very long time.”

A strain of hantavirus was first diagnosed in the 1950s in the Hantan region of Korea, as 3,000 U.S. servicemen fighting the Korean War came down with something then called hemorrhagic fever. Of those, 190 died.

Hantavirus again caught the public eye in 1993, when an outbreak surfaced near the Four Corners area of New Mexico, sickening and killing dozens of people there and elsewhere.

In California, there have been 13 confirmed cases of hantavirus in people. Eight died.

Since the outbreak in the Southwest three years ago, California launched a statewide campaign, trapping and testing nearly 5,000 animals in a search for those carrying hantavirus.

Biologists found the virus predominantly in deer mice in the counties of Los Angeles, Orange, Santa Barbara, Kern--and now Ventura.

County biologists laid traps last year near Fillmore, Ojai, Lockwood Valley and Ventura but found no hantavirus. Recently, they laid another series of traps in the foothills just south of the Wood Ranch subdivision.

“We use Sherman traps, which are small aluminum boxes that catch the animal live,” said Randall Smith, county environmental health specialist. The bait: Quaker Oats.

“We anesthetize [the mice] and take a blood sample from them,” he said. “Then they are put down [destroyed] in the field. The carcass is kept, and if the blood sample comes up positive, we take other tests . . . to get more information on the disease.”

In Simi Valley, at the end of Wood Ranch Parkway, health officers laid 50 traps. They caught, drugged and killed 21 deer mice.

And the subsequent blood samples showed that two of the mice carried traces of hantavirus, said Robert Gallagher, vector control officer for the Ventura County Department of Environmental Health.

“We put out this [information] not to overtly alarm the public,” he said. “We just wanted to inform them that when they enter into certain areas, they need to take simple precautions to avoid exposure.”

Hantavirus, Gallagher said, is perhaps harder to catch than bubonic plague, a bacterial infection carried by fleas and curable with antibiotics.

“For bubonic plague, you have to be bitten by an infected flea,” Gallagher said. “With hantavirus, you have to breathe in enough of this virus-laden dust to get a sufficient dose. I don’t think they know what that dose response is.”

Bubonic plague--the infamous disease that killed millions in Europe from the Middle Ages through the 14th century--forced county health officials to close certain public campgrounds several times over the past four years.

Health officials closed the Chuchupate Campground in Los Padres National Forest in 1993 and 1994 after biologists found rodents infected with plague.

Wheeler Gorge Campground near Ojai was closed last year, and again last month, after ground squirrels and other wild rodents were found to be carrying plague bacteria. In the past 22 years, Smith said, at least two county residents have died after contracting bubonic plague, the last in 1984.

But the hantavirus is far more deadly, killing about half the people it infects, Davis said.

“With that kind of fatality rate, it’s not that far behind Ebola and some of those others,” he said. “So we take it very seriously.”

People should wear dust masks and rubber gloves when cleaning out summer cabins, shacks or other buildings that have been infested by deer mice, he said.

Davis said a worried Ventura County doctor phoned him Wednesday morning after cleaning out a camper that had been heavily infested by rodents.

“I think he was a little nervous,” Davis said. “I told him to be aware of what the symptoms are. And if they start to develop, he knows what to do. . . . Most of the people who have [died] didn’t know what they had, they didn’t have a clue. They thought they had a severe case of flu and just tried to tough it out.”

On the other hand, Davis said, exposure is no guarantee of infection. A survey of 3,000 public health officers across the nation found hantavirus antibodies in the systems of only two people, he said.

“Which probably points out, again, that this is an extremely hard disease to catch,” he said.

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Avoiding hantavirus:

* Stay away from rodents dead or alive, rodent droppings and urine.

* When camping, pitch tent in areas without droppings, avoid rodent dens, drink only disinfected water and sleep on a ground cover and pad.

When you must work in areas where hantavirus contact is possible:

* When opening unused cabin, shed or other building, open all doors and windows, leave the building and let it air out for 30 minutes.

* Return to building and spray surfaces, carpet and other areas with disinfectant. Leave building for 30 minutes more.

* Spray mouse nests and droppings with 10% solution of chlorine bleach or strong disinfectant, let sit 30 minutes, don dust mask and rubber gloves to put the materials into plastic bags, seal and dispose of bags in trash or incinerator. Dispose of gloves, mask and cleaning materials in same manner.

* Wash all potentially contaminated hard surfaces with bleach or disinfectant solution.

* Avoid vacuuming. Vacuum filters are too coarse to trap virus particles. Vacuum only after area is thoroughly decontaminated, and then (for the first few times) only with mask and adequate ventilation.

* If you must pick up a dead rodent, handle it only with rubber gloves or plastic bag, put carcass into plastic bag, seal it and dispose of in trash or incinerator.

Source: Centers for Disease Control, California Department of Health

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The Hantavirus

Since 1993, testing by California health officials has found hantavirus in the counties of Los Angeles, Santa Barbara, Orange, Kern and now Ventura.

* Symptons: Flu- like, chills, muscle aches, nausea, vomiting, red eyes and shortness of breath, eventual respiratory failure.

* Transmission: Rodent borne, usually in rural settings, no evidence of transmission between people.

* Treatment: Experimenting with antiviral drugs, not conclusive yet.

Source: Centers for Disease Control.