CONTACT: DAVE PEDERSEN
283 Medical Laboratories
Iowa City IA 52242
(319) 335-8032; fax (319) 335-8034
UI Hygienic Lab offers tips for guarding against hantavirus infection
IOWA CITY, Iowa -- During the fall and winter months, houses or outbuildings
can provide a haven for mice and other rodents. They're a nuisance for
sure, but they pose a more serious health risk: the spread of hantaviruses.
Hantaviruses include several different strains, some of which cause
hantavirus pulmonary syndrome (HPS). This life-threatening disease is marked
by flu-like symptoms -- high fever, severe body aches, chills, troubled
breathing and cough -- which progress rapidly to severe lung disease. There
is no known cure or vaccine for HPS. In the United States, the disease's
mortality rate is high -- about 37 percent.
The illness first made headlines in 1993 when health officials in the
Southwestern United States investigated a cluster of deaths among young
people in the region. Researchers learned that the disease was caused by
a hantavirus and transmitted by infected mice. Since then, more than 170
cases of the illness have been identified among humans in 28 states.
The first confirmed case of HPS in Iowa occurred last spring and caused
the death of a north-central Iowa man who resided in a rural area near
There are at least 10 strains of hantavirus worldwide, of which four
have been identified as causing HPS in humans. The primary carrier of the
HPS strain is the deer mouse. It is four to nine inches in length from
head to tail and ranges in color from pale gray to reddish brown, with
white fur on its belly and feet. The deer mouse is highly adaptable and
is found in different habitats, including human residences and rural areas,
but generally not in urban areas.
"The virus is transmitted mainly in the airborne particles of rodent
urine, droppings or saliva," says Dr. Tom Gahan, virologist at the
University of Iowa Hygienic Laboratory. "However, transmission also
may occur when fresh or dried materials contaminated by rodent droppings
come into contact with broken skin, are introduced into the eyes or, possibly,
ingested in contaminated food or water. People also have become infected
after being bitten by rodents." In South America, a strain of the
HPS virus appears to be transmissible from human to human, but this has
not been documented in the U.S.
"Researchers at the Centers for Disease Control and Prevention
(CDC) have implicated strain differences to account for this distinction,"
says Dr. Mary Gilchrist, director the UI Hygienic Laboratory, "but
we still have a lot to learn about this disease."
Last August, Mike Birmingham, a field researcher at the Hygienic Laboratory,
and researchers from the CDC, the Iowa Department of Public Health and
Iowa State University spent three days collecting blood, tissue and organ
samples from rodents on the farmstead of the Alden man who died from HPS.
The researchers trapped about 25 rodents, including deer mice, whitefooted
mice, shrews and prairie voles. Shrews are not known to carry hantaviruses,
Birmingham notes, while voles are known to carry some strains of hantavirus,
but not the strains that cause HPS in humans.
The Hygienic Laboratory and the CDC divided the rodent samples, and
both laboratories did analyses to compare results. They did not find the
HPS-causing strains in the mice they had collected, but did detect in two
vole samples antibodies to a hantavirus strain that's currently being studied
to see if it causes the disease in humans.
"Actually, the people from the CDC weren't all that surprised,"
Birmingham says, "because we just didn't catch that many mice for
testing. With the '93 outbreak in the Southwest, there was a massive infestation
of mice, probably due to climatic factors."
Some scientists have speculated that hantavirus infection in the U.S.
is prevalent during wet weather seasons, particularly pronounced El Niño
years, Gilchrist notes. "If this is the case, we might see more infections
in humans this winter," she says.
People at a higher risk for hantavirus infection include families who
move into homes, particularly in rural areas, that rodents have infested;
campers and hikers; electricians, plumbers and others who work in crawl
spaces; and farmers who clean barns, outbuildings and grain storage areas.
"Especially in the fall and winter, as rodents look to move indoors,
people need to be aware. The best prevention is to keep all rodents from
entering your home and to carefully clean and disinfect areas where rodents
have been detected," Gilchrist says.
The Hygienic Laboratory offers these tips for guarding against hantavirus:
* Keep your home and/or any outbuildings clean. Keep all grains or other
edible materials like birdseed in rodent-proof cans. Eliminate storage
of stuffed furniture or other potential sources of rodent bedding in outbuildings.
Ventilate all areas of the house or outbuildings before cleaning.
* Prevent rodent entry and dispose of any rodents in your home. Use
steel wool or cement to seal any holes in your house.
* Use outside control measures. Cut grass and brush within 100 feet
of the house. Move woodpiles, gardens, trash cans and animal feeders at
least 100 feet from the house.
* Disinfect areas where rodents may have been. Always wear rubber gloves
during cleanup. To minimize dust, do not vacuum or sweep before mopping.
For more information on hantaviruses and HPS prevention, contact the
UI Hygienic Laboratory at (319) 335-4500, or the Iowa Department of Public
Health at (515) 281-5787. Hantavirus information from the CDC can be found
by calling 1-800-532-9929 or visiting the CDC World Wide Web page at http://www.cdc.gov.