Deer mice spread virus in the Sierra |

Deer mice spread virus in the Sierra

Summertime in the Sierra usually includes camping, swimming, hiking and other outdoor activities. Unfortunately, these popular pastimes bring people into contact with all sorts of wildlife, including the deer mouse – one of the main rodents carrying the hantavirus.

Deer mice shed the virus in their urine, droppings and saliva, according to the Center for Disease Control, and it is transmitted to people through the air – a process called aerosolization.

Aerosolization occurs when the droppings or urine are stirred up, which causes tiny droplets containing the virus to become airborne.

In the case of Hugh Williams – the Truckee man infected with hantavirus July 10 – Nevada County health officials said aerosolization occurred as he swept out his camper shell.

There are several other ways the virus can spread. Although very rare, the disease can be spread to a person if they are bitten by an infected mouse. Also, researchers believe you can become sick if you touch an object already contaminated with the virus, then touch your nose or mouth.

Although not proven, researchers also suspect it is possible for an infected deer mouse to contaminate human food.

Hantavirus stops at the person who has been infected – it can’t be passed from one person to another. CDC officials said you can’t get the virus from touching or kissing a person who has the disease, or from a healthcare worker who has treated an infected person.

Also, you cannot become infected from a blood transfusion in which the blood came from a person who had the disease and survived.

Researchers said you cannot get the disease from other animals – only rodents. Farm animals such as cows, chickens and sheep and insects such as mosquitoes do not carry the virus. Also, dogs and cats do not transmit the disease, however, they can put people at risk if they catch infected rodents.



— keep a clean home, especially the kitchen. Wash dishes, clean counters and floors and keep food covered in rodent-proof containers.

— keep a tight-fitting lid on garbage; discard uneaten pet food at the end of the day.

— set and keep spring-loaded rodent traps. Set traps near baseboards because rodents tend to run along the walls and tight spaces.

— set EPA-approved rodenticide with bait under plywood or plastic shelters along baseboards.

— seal all entry holes 1/4 inch wide or larger with steel wool, cement, wire screening or other patching materials.


— clear brush, grass and junk from around house foundations to eliminate a source of nesting materials.

— use metal flashing around the base of wooden, earthen or adobe homes to provide a strong metal barrier. Flashing should be installed so that it reaches 12 inches above the ground and six inches beneath the dirt.

— elevate hay, woodpiles, and garbage cans to eliminate possible nesting sites. If possible, locate them 100 feet or more from your home.

— trap rodents outside. Poisons or rodenticides may be used.

— encourage natural predators such as non-poisonous snakes, owls and hawks.

Cleaning infested areas:

— wear latex rubber gloves.

— don’t stir up dust by sweeping or vacuuming droppings, urine or nesting materials.

— thoroughly wet contaminated areas with detergent or liquid to deactivate the virus. Most general purpose disinfectants and household detergents are effective. For larger areas, use a 10 percent household laundry bleach solution (three tablespoons of bleach per gallon of water).

— Once everything is wet, take up contaminated materials with a damp towel, then mop or sponge the area with disinfectant.

— spray dead rodents with disinfectant, then double-bag the animals with the cleaning material and burn or bury them. If burning or burying is infeasible, contact the Nevada County Health Department at 265-1450 for other disposal options.

— disinfect gloves before taking them off with disinfectant or soap and water. After removing the gloves, wash your hands with soap and warm water.

(Source: The Centers for Disease Control and Prevention – CDC)

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