First Case Reported in Colorado Serves as Warning to Take Precautions Against Hantavirus

DENVER -- An early case of hantavirus in Colorado this year has prompted the Colorado Department of Public Health and Environment to remind residents of the state of the importance of taking precautions to avoid exposure to this severe respiratory illness.

A La Plata County man was hospitalized in mid-March with an illness later confirmed to be hantavirus. The hantavirus case, the first in Colorado in 2005, is under investigation by the San Juan Basin Health Department and the Department of Public Health and Environment.

Hantavirus Pulmonary Syndrome is a disease caused by a virus carried by a particular type of mouse, the deer mouse. Deer mice can be found throughout Colorado, but are most common in rural areas. Deer mice are brown on top and white underneath, with large ears relative to their head size. House mice on the other hand are all grey and have small ears.

John Pape, an epidemiologist specializing in animal-related diseases for the Department of Public Health and Environment, explained that while hantavirus cases can occur at any time of the year, they usually occur in the spring and summer as the weather warms and foliage becomes more abundant.

Pape said, "This early season case serves as a reminder for people to take simple precautions to avoid exposure to hantavirus when opening cabins and doing spring cleaning. It is expected that mouse populations may be high this year due to the increased moisture in many areas of the state."

He explained that during the recent drought in the state, plant and seed growth was reduced, limiting the natural food supply for mice and other rodents.

"However, with more moisture, it's a different story," he said. "There is a direct link. More food equals more mice. With the return of moisture comes lush growth of plants which provides abundant food for rodents and can result in a population boom."

Pape said that many of the patients who have had hantavirus reported that before they became ill, they saw a dramatic increase in the number of mice around their home.

"An unusually large number of mice or a sudden increase in the population should be a warning sign of increased risk of hantavirus exposure," he warned.

Pape said, "Infected deer mice shed the virus in urine and feces. Humans are infected when they inhale dirt and dust contaminated with deer mice urine and feces. This can occur when people have contact with infected mice that have invaded their homes or by stirring up dust while working in or cleaning out rodent-infested structures such as barns; garages; storage sheds; trailers or cabins.

In 2004, there were four hantavirus cases in Colorado, including one death.

In 2003, there were five hantavirus cases in the state, including a fatality involving a 22-year-old man from Adams County who died on January 11, 2003. The other four persons recovered.

In 2002, there was only one hantavirus case in Colorado. There were none in 2001. However, in 2000, there were eight hantavirus cases in Colorado, including three deaths, and in 1999, there were four cases, and one death.

Pape urged people to be particularly careful when there is evidence of a heavy, active mouse infestation such as the presence of mouse droppings or nests; damage caused by mice; or live mice being seen in and around the buildings or nearby wood or junk piles.

"As people begin cleaning out barns, garages, storage buildings, trailers or cabins that have been closed up all winter, they need to take precautions before beginning such work, particularly if there are signs of mice," he said.

He provided tips for the public to take to minimize their exposure to hantavirus when cleaning potentially contaminated areas. The tips included:

Before entering rodent-infested structures that have been closed for more than a month, open doors or windows to provide good ventilation for 30 to 60 minutes. If there appears to be a large number of live mice present, use traps or poisons to reduce the mouse population before cleaning, if possible.

Ventilate the structure before and during cleaning. Avoid stirring up dust by spraying mouse droppings, nest materials and carcasses with a mixture of bleach and water. A bleach mixture of one cup of bleach per gallon of water is recommended.

Use rubber gloves to pick up saturated waste, including nesting materials or dead mice. Bag the waste using plastic bags, and bury or dispose of it in an outdoor garbage can or landfill.

In cases of severe infestation, or when ventilation and dust suppression are not possible, use a rubber face mask equipped with a High Efficiency Particulate Air (HEPA) filter.

Seal all holes or openings larger than one-fourth inch to prevent mice from entering a building. Install weather stripping under doors, including garage doors.

Store food, including pet food and livestock feed, and garbage in rodent-proof containers. Rodent populations are determined by the availability of food sources so just eliminating food supplies will reduce the number of mice.

Remove rodent hiding places such as wood, junk and brush piles. Store firewood at least 100 feet from the house. Keep bushes and vegetation around structures well trimmed and grass cut short.

In rural areas or structures with mice infestations, rodent control, using traps and poisons, should be conducted on a year-round basis.

When camping, avoid sleeping on bare ground. Instead, use tents with floors or cots.

Source: Colorado Department of Public Health