The Heat Is Online

CDC: Extreme Weather Fuels Hantavirus Rise

U.S. sees upsurge in rodent-borne illness

Hantavirus reported in 30 states
Reuters News Service
June 28, 1999

ATLANTA - U.S. cases of an often-fatal respiratory illness first recognised in 1993 rose sharply this year because weather conditions allowed the mice that most often spread the disease to flourish, health officials said today.

The federal Centres for Disease Control and Prevention (CDC) said that there were 18 suspected or confirmed cases of hantavirus pulmonary syndrome during the first five months of this year, compared with an average of two cases during the same five-month period in 1995 through 1998.

James Mills, chief of a medical ecology unit in the National Centre for Infectious Diseases, said the cases reported this year "are more cases than we have seen for this period in any year since we've been monitoring the disease."

Of the 217 people who have developed the disease since 1993 in 30 states, 43 percent have died, the CDC said. The rodent-borne illness first attracted attention when it killed 11 people in northwestern New Mexico in 1993.

The deadly lung infection is caused by a hantavirus carried by rodents and passed to humans through infected rodent urine, saliva or droppings. A primary symptom is difficulty in breathing caused by fluid buildup in the lungs. It quickly progresses to an inability to breathe.

Mills said rainy weather followed by a mild winter contributed to an increase in the population of deer mice, the primary carrier of the virus that causes the illness.

"In 1997, there was an El Nino event which brought unusual quantities of rainfall to the usually dry southwestern United States. This resulted in increased vegetation greenness, improved habitat and increased food quality for the deer mouse population," Mills said.

"Populations reached very high densities by the spring of 1998 in response to this. What has happened in 1999 is that we had a relatively benign winter. A high percentage of the population survived over the winter," he said.

Mills said increased population densities have led to more transmission of the virus between deer mice "which results in increased chances of humans coming into contact with infected mice."
The sooner someone with the lung infection seeks medical treatment, the better the chance of recovery, he said.

"The probability of surviving this disease is proportional to how quickly one is hospitalized and enters into intensive care, which may involve supplemental oxygen," Mills said.

Confirmed cases of hantavirus pulmonary syndrome have been reported this year in Colorado, New Mexico, New York and Washington. Suspected cases with preliminary evidence of the illness have been reported in Arizona, California, Idaho, Iowa, Montana, New Mexico and Washington, the CDC said.

Reuters News Service

Deadly Virus May Lurk In the Cutest Little Mouse

Wall Street Journal, June 21. 1999

If summer escape to a country place beckons, consider this tale of mice and men. Drake Hunter, the seven-year-old son of a U.S. Airways pilot, scooped up a newborn mouse from a sand dune on the Memorial Day holiday. Enchanted, he named the mouse Squeaky.

Alarmed when the critter left droppings in her son's hands, Julie Hunter remembered news of rodent viruses near their vacation spot on California's Channel Islands off the Ventura coast. The mouse was whisked to a state health lab for antibody testing. The test was positive. Drake is still being closely watched.

They're back, and they're spreading: hantaviruses, a family of microbes harmless to mice but potentially fatal to humans.

"This year seems to be starting off to be a very big year," says disease sleuth C.J. Peters, head of the Special Pathogens Branch of the U.S. Centers for Disease Control and Prevention in Atlanta. In recent months, he adds, the CDC has seen more cases than average of hantavirus pulmonary syndrome, the lethal lung infection first identified in the U.S. in 1993.

Inhaling even the tiniest particles of rodent waste from a dusty cabin, basement or crawlspace can trigger disease. What begins as a raging flu -- with cough, fever, aches, malaise and nausea -- leads swiftly to respiratory failure and death in 45% of cases. There is no cure, though clinical trials of the antiviral drug ribavirin continue. Many victims -- healthy young adults -- die despite intensive care.

Geographically, cases are spreading, too. The first known hantavirus outbreak in the U.S. occurred six years ago in the Navajo country of Four Corners, where Arizona, New Mexico, Utah and Colorado converge. By last month, hantavirus pulmonary syndrome had sickened 217 people in 30 states including New York, California, Texas, Georgia, Florida, Washington, Idaho and Iowa. Eleven new reports now await confirmation.

One man became ill this year when he tried a barehanded collection of trapped mice from a hunting cabin in Sullivan County, N.Y. He survived. But two earlier New York victims -- a college student and a landscaper on eastern Long Island -- died in 1994 and 1995.

CDC and state health officials are braced for a resurgence of the disease because warm, wet winters have enriched the grassy habitats that nourish rodent colonies. Prevalence of the virus is rising as well.

Near Durango, Colo., new studies are finding 40% of mice are infected, says 27-year CDC veteran Charles Calisher, now professor of virology at Colorado State University in Fort Collins. "We were shocked," he says.

To complicate matters, hantaviruses and their hosts are diversifying. Western deer mice harbor a hantavirus species named Sin Nombre, Spanish for "no name." In the East, ubiquitous white-footed mice (infamous carriers of Lyme disease) harbor hantavirus species called New York virus and Monongahela virus. In the South, Black Creek Canal virus and Bayou virus infect cotton rats and rice rats in Texas, Louisiana and Florida. All are hantavirus members.

If you're planning to open a cabin or country retreat that was sealed for the winter, here's the expert prescription for demousing. Don't sweep or vacuum infested areas, because this blows dust into the air. Don't allow children or anyone else to root around in basements, attics, under porches, in crawlspaces or around wood piles where dried mouse droppings could be inhaled.

Air out the house before anyone enters. Then, the CDC says, douse any areas of mouse infestation with a 10% solution of chlorine bleach, which kills the virus and prevents dried particles from becoming airborne. Wear boots, gloves, mask and protective clothing while wiping up waste with wet paper towels or cloths. Bag and discard them.

The New York State Department of Health recommends wearing respiratory masks with a HEPA or N-100 filter, plus protective eye gear. Inexpensive painters' masks aren't effective. Around the house, remove food sources, brush and woodpiles that attract

and shelter mice. Seal cracks and chinks that invite wintering rodents. Set snap traps inside bags, so animals can be discarded without touching.

Sorry, but experts advise against using humane traps and releasing the animals. Mice can home in on your home from a distance of 1,100 yards. "If you release them, they'll be right back," says Dr. Calisher.

If you've been near mice and get ill, seek immediate medical care and tell doctors you're concerned about hantavirus pulmonary syndrome, or HPS. Remember, the incubation period can range from three days to six weeks. In Oxnard, Calif., Mrs. Hunter urges, "Go to the hospital. Don't wait."

One harrowing dawn, 10 days after his encounter with Squeaky, her son Drake spiked a fever. "Ask me about panic," she says. It turned out to be a simple cold or flu.

Drake's antibody test was negative, and other blood work has remained normal so far. But due to the disease's long latency, he'll remain under close watch for several more weeks.

Expert on outbreaks from Ebola to Lassa fever, the CDC's Dr. Peters says it's hard to resist winsome wild creatures. "Those little guys are cute," he agrees. "But we have to persuade people to just look, and rely on Disney for their up-close-and-personal experiences."

For her next vacation in mouse country, Mrs. Hunter agrees, "I'll pack latex gloves."

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