Hanta Virus

The disease known as Hanta Virus Pulmonary Syndrome has been identified as a health risk to the general population. Danger of infection is specifically associated with the deermouse. Other rodents may also be carriers.

Although the risk of infection is slight, the Hanta Virus is potentially lethal. Half of the people infected by the virus have died. At least one death has been attributed to the disease in Ontario. The victim contracted the virus after cleaning out a cottage that had been infested by mice.

Rodent nesting materials, burrows, droppings, and the surrounding environment present the greatest risk of infection The danger is higher in an enclosed environment -- e.g. granaries, feed rooms, and other storage areas. Rodents may also nest over winter in farm equipment such as combines and balers.

Direct contact with rodents will increase the risk of infection. Disease transmission most commonly occurs when rodent droppings are disturbed and the resulting dust is inhaled.


The average time between contact with the virus and the onset of illness is two to three weeks. Unfortunately, the initial symptoms are non-specific. They include fever, muscle ache, cough, headache, nausea, and vomiting -- very much like the flu.

If you develop a fever or respiratory illness that is rapidly worsening and includes shortness of breath, seek immediate medical attention. Inform the doctor that you have been in contact with rodents, and suspect possible Hanta Virus infection.


To minimize risk of Hanta Virus infection, rodent populations must be controlled.

  • General cleanliness is very important.
  • Get rid of trash, abandoned machinery, discarded tires, and other items that could serve as rodent nesting sites.
  • Use commercial traps, rodenticides, or ultra-sonic devices.
  • Seal all openings of more than a quarter-inch diameter. Use metal flashings at the base wooden or earthen structures. Gravel under structures helps prevent burrowing.
  • Keep food and garbage in rodent-proof containers. Trash should be disposed of promptly.
  • Cut grass, brush and dense shrubbery within 100 feet of buildings.
Even with the most fastidious control program, some contact with rodents and/or their droppings is inevitable on the farm. Infested facilities need to be cleaned up before entry and use. It is critically important to protect your respiratory system and skin when handling dead rodents, droppings, nesting materials, and other areas of contact. Observe the following precautions:
  • Any enclosed area should be aired out for at least 30 minutes before cleanup begins.
  • Always wear rubber gloves when cleaning up rodent carcasses and droppings, or when handling traps.
  • Wear a respirator that has a HEPA (P100) rating. Ordinary dust masks will not filter the virus!
  • If there is evidence of a lot of rodent activity, wear disposable coveralls. Any exposed clothing should be washed separately from the regular family laundry. Handle clothing with gloves. Wash in hot water and detergent, and dry in a hot dryer.
  • Before starting cleanup, thoroughly wet down the area with a 10 percent household bleach solution (3 tablespoons of bleach in one quart of water).
  • Use only wet cleaning techniques, such as damp mopping. Avoid sweeping, vacuuming and other dry cleanup techniques.
  • Double bag rodent carcasses and other solid materials in a 10 percent bleach solution. Dispose of the bagged material by burning or burial.
  • After cleanup, disinfect the entire area with a 10 percent bleach solution. Allow the area to dry thoroughly before entry or use.
  • All traps should be disinfected in a bleach solution.
  • Before removing rubber gloves, wash them in a bleach solution, and then with soap and water. Wash your hands upon removal of the gloves.
Although the Hanta Virus is not particularly hardy, it is potentially lethal. All rodent-contaminated materials should be treated as infected. If you have any reason to suspect that you have been infected by Hanta Virus, seek immediate medical attention. Survival chances are enhanced by early treatment of the disease.

A Quick Guide to dealing with Hanta Virus is available from the Farm Safety Association's Guelph office. For more information about this dangerous disease, contact your local public health office.

This Hanta Virus Guide, available from the Farm Safety Association, details safe cleanup procedures.

Disclaimer and Reproduction Information: Information in NASD does not represent NIOSH policy. Information included in NASD appears by permission of the author and/or copyright holder. More