Hantavirus has been in the news a lot lately. Betsy Arakawa, wife of the late actor Gene Hackman, recently passed away in New Mexico due to the disease and California has already seen 3 hantavirus-related deaths this year. In this article we share information to help you understand hantavirus and what you can do to protect yourself and your community.

What is Hantavirus and how is it spread?

Hantaviruses are a group of viruses that some rodents carry. In California, deer mice are the primary carriers of hantavirus. While human cases are rare, they can be fatal.  

Deer mice shed the virus in their saliva, urine, and droppings. A person may be exposed to hantavirus by breathing contaminated dust after disturbing or cleaning rodent droppings or nests, or by living or working in rodent-infested settings. Rarely, individuals can also be infected by 1) consuming food contaminated with rodent urine or droppings; 2) touching surfaces where rodents have been and then putting their hand in their mouth; or 3) being bitten by an infected rodent. There is no evidence that North American hantaviruses spread from one person to another.

Where is Hantavirus common in California?

Hantavirus is most common in the eastern, mountainous regions of the state. Most cases have been reported from Mono, Inyo, and Mariposa counties. 

Since deer mice prefer forests, grasslands, and agricultural areas, they aren’t normally found within urban and residential areas unless fields, forests, or other suitable habitats surround those areas. As communities expand into wildland areas, deer mice, and other similar species, may be seen more often in and around homes, cabins, or other structures.  

For more about hantavirus including a map of reported cases, see the California Department of Public Health website at https://www.cdph.ca.gov/Programs/CID/DCDC/pages/hantaviruspulmonarysyndrome.aspx#.

How to identify deer mice

Deer mice, Peromyscus maniculatus, are the most abundant and widely distributed mammal in North America. They look similar to the house mouse, Mus musculus, but can be distinguished by their bicolored tail, larger eyes, and white undersides.

Safely cleaning rodent-infested areas

Once deer mice are discovered infesting a dwelling, it is critical to avoid working and sleeping in these areas until the infestation has been controlled and the area has been made safe for humans. 

Before occupying an infested building, open the doors and windows to air out the room for at least 30 minutes. Where possible, use an electric fan on windowsills and in door entrances to assist the process. Be sure to vacate the building during the ventilation process to prevent inhaling aerosolized particles. Never stir up dust by vacuuming or sweeping or through any other activity. Consider wearing a respirator or face mask with a high efficiency particulate air (HEPA) filter if cleaning heavily infested areas. 

It is important to wear nonfabric gloves (e.g., rubber, latex, vinyl, or nitrile) when cleaning up deer mouse infestations. Thoroughly soak contaminated areas including deer mice in traps, droppings, and nests with a disinfectant solution such as a 10% hypochlorite (bleach) solution or an EPA-registered disinfectant. Once everything has soaked for the amount of time specified on the disinfectant label, remove all nest material, deer mice, and droppings with a damp paper towel and place them in doubled plastic bags. Then, mop or sponge the area with the disinfectant solution. Upholstered furniture and carpets can be shampooed and steam cleaned. Once finished, remove gloves and dispose of them along with the other materials in a covered trash can that is regularly emptied. After removing the gloves, it is important to thoroughly wash hands with soap and water or use a waterless alcohol-based hand sanitizer when soap is unavailable.

For additional information on rodent cleanup, visit the Centers for Disease Control and Prevention website at https://www.cdc.gov/healthy-pets/rodent-control/clean-up.html.

Deer mice management 

There are no rodenticide baits registered for controlling deer mice in residential settings. Instead, control residential deer mouse infestations using traps, excluding mice from structures by sealing all small gaps and cracks, and storing all food items securely in rodent-proof containers. 

Repellents, frightening devices, and natural predators (cats, coyotes, owls, etc.) will not prevent or eliminate deer mice problems or reduce the risk of hantavirus infection. Avoid contact with all wild rodents, their droppings, and nesting materials. 

See Pest Notes: Deer Mouse for more information on managing deer mice.