Deer Mice and Hantavirus. What You Need to Know

A deer mouse is about the size of a common house mouse. Its coat runs from pale gray to deep reddish brown, and the tail is sharply two-toned, white below and dark above.⁵ Deer mice also have larger eyes and a white underside, while a house mouse is gray all over.⁷

The white-footed mouse looks close. It is pale to rich reddish brown on top with a white belly and white feet, and its tail is usually shorter than its body.⁶ Both are Peromyscus mice and both are named as hantavirus reservoirs in the United States.⁴

Do not try to tell them apart in a wall. Treat any wild mouse with white on the belly with care. For gray mice in the kitchen, see house mice or the mice and rats hub.

Deer mice have 2 to 4 litters a year. A litter can hold 1 to 11 young, though the average is five or six.⁵ They nest in burrows, trees and buildings.⁵

White-footed mice also have 2 to 4 litters a year during a breeding season that runs between March and June. Litters are two to six young born after a 22 to 28 day pregnancy.⁶

These mice live outside most of the year. They eat seeds, fruits, flowers and insects, and they are found in forests, grasslands, brushlands and farm fields.⁵ They move into sheds, cabins and garages when the nest spot is warm and dry.⁶

The signs look like any mouse problem, so assume wild mice in any shed, cabin or barn.

• Droppings in drawers, cupboards, sheds and cabins.
• Nests of shredded fibrous material in warm, dry places such as boxes and old vehicles.⁶
• Gnaw marks and tracks.⁷
• Mice that live in a closed building through the winter.³

Look at the dust, not just the droppings. The danger is dried urine, droppings and nests that get stirred up into the air.³ If you see a mess in a space that has been shut, do not start with a broom.

Hantavirus can be deadly. Infection starts with fatigue, fever and muscle aches 1 to 8 weeks after contact. Later symptoms such as cough and shortness of breath follow 4 to 10 days later. CDC says 38% of people who develop respiratory symptoms may die.¹ The Ohio Department of Health puts the mortality rate of the lung syndrome at about 40 to 50%, and says patients often need hospital care within 24 hours once the lung phase begins.⁴

People get it by breathing air contaminated when fresh urine, droppings or nesting material is stirred up, or when saliva, urine or droppings get in cuts or the eyes, nose or mouth. A bite can also spread it.⁸ Risk climbs in small, closed spaces.³

It is not common. California reports about 3 infections a year.³ There is no specific treatment, but early medical care helps.³

Clean wet, never dry. Follow the CDC steps.

1. Open all doors and windows for 30 minutes and leave the area.²
2. Put on rubber or plastic gloves.²
3. Soak urine and droppings with disinfectant, or 1.5 cups of bleach in 1 gallon of water, until very wet. Let it sit 5 minutes.²
4. Wipe up with paper towels and put them in a covered garbage can. Mop hard surfaces with disinfectant.²
5. Spray dead rodents and nests, bag them, then double bag and knot both bags.²
6. Wash gloved hands, take off the gloves and wash with soap and warm water.²

Never sweep or vacuum droppings or nests.² To remove the mice, use snap traps, not glue or live traps.³ House mouse details are in the house mouse guide.

Cleanup with bleach and gloves costs little, so most of the cost is stopping the mice. A pro mouse job usually runs $150 to $550, with an average near $350. Some charge $75 to $125 per visit, and after-hours calls add $100 to $200.⁹

Snap traps run $3 to $6 each. Bait stations cost $8 to $20.⁹

Severity, home size and location move the price. Mice in the walls need more visits, and sealing entry points costs more now but may save money later.⁹ The guide we used gives no price for hantavirus cleanup alone, so ask any pro what the cleanup includes.

The best prevention is to keep wild rodents out. CDC calls rodent control the primary strategy against hantavirus pulmonary syndrome.⁸

• Seal holes the width of a pencil or larger.³
• Set snap traps, and skip glue and live traps.³
• Store all food in rodent-proof containers.³
• Air out closed cabins, sheds and outbuildings for 30 minutes before you go in to clean.²
• Wash contaminated bedding, clothing and stuffed animals in hot water with detergent.²
• Trap and seal before you clean, so new mice do not undo the work.

Pet rats are not recommended for households with children 5 or younger, pregnant women or people with weakened immune systems.⁸

The risk peaks when you disturb old nests. CDPH says the chance of infection rises when you open or clean buildings in rural areas that were closed for winter and where deer mice have entered.³ That makes spring the time to be careful.

In Ohio, the white-footed mouse breeding season runs March to June, which is why the grid rises in those months.⁶

Wild mouse numbers do not drop to zero in winter, so a cabin you shut in October can hold a nest by April. Open it, air it out for 30 minutes and then clean it wet.²

Ohio has deer mice and white-footed mice, and both are named hantavirus reservoirs in the United States. The Ohio Department of Health says the deer mouse occurs in Ohio, but there have been no confirmed cases in the state.⁴ Most U.S. cases, 95%, came from states west of the Mississippi River.⁴

White-footed mice live in many habitats but are most often found in woody or brushy areas, and they are the most abundant rodent in mixed forests and edges of farm fields.⁶

That means an Ohio barn or hunting shed will often hold white-footed mice. Use the same wet cleanup steps for any wild mouse mess.²

Deer mice live throughout California, and Sin Nombre virus is the hantavirus that can make people sick in the state. Andes virus is not found in California.³ About 3 Sin Nombre infections are reported each year.³

CDPH says the best prevention is to keep wild mice out of homes, cabins, sheds, cars and campers. Seal holes the width of a pencil, use snap traps and store food in rodent-proof containers.³ Clean with a fresh 10% bleach solution after you air out the space for 30 minutes. Do not sweep or vacuum.³

Hire a licensed pest company for a heavy infestation. See the mice and rats hub for how to check a California license.