Hantavirus is carried by some mice and may be transmitted through contact with their droppings. Most cases occur in the spring during cleaning when people may breathe in air borne particles.
- Early symptoms are similar to the flu, but can quickly develop into severe breathing problems and in some cases hantavirus infection can be fatal.
The incidence of the hantavirus and the risk it poses to the public is low. However, particularly in the spring, when the weather improves and people spend more time outdoors and doing spring cleaning, remember to keep any risk to a minimum and take precautions to avoid hantavirus infection.
The only confirmed carrier of the hantavirus in Alberta is the deer mouse (reddish-brown or in some cases grey, but always with white fur on the underside of the neck, belly, feet, and tail). However, it is possible that other rodents may carry the virus and it is not always easy to determine what kind of mouse one is exposed to (particularly when the only evidence is droppings). The virus does not appear to have any effect on mice which carry it.
- All rodents should be treated as potential carriers.
The main risk of infection comes from being exposed to accumulations of mouse droppings in enclosed areas — for example, cleaning a garage or shed that mice have been living in during the winter. Hantavirus is passed to humans when they breathe in airborne particles released from the droppings, fresh urine and nesting material of infected rodents.
The virus does not appear to cause any illness in pets. Even if they are exposed to the virus, dogs and cats do not pass the infection on to their owners. The virus is also not passed from one person to another.
- The most effective precaution against infection is to keep rodents out of homes and work areas, and immediately trap any that get in.
- Ventilate enclosed areas before cleaning by opening doors and windows for at least 30 minutes. Stay out of the area while it airs out.
- When you begin cleaning, disturb as little as possible, mouse droppings and nesting material.
- Wear rubber gloves to handle the droppings. Rinse the gloves in disinfectant (such as bleach solution or soap and water) before taking them off.
- Soak droppings with disinfectant (1.5 cups bleach to 1 gallon water) before you mop them up or pick up with a paper towel. Place them in a sealed bag and bury it, or put it out for removal in garbage cans with tight-fitting lids.
- Do not sweep or use a vacuum cleaner to remove droppings in an enclosed space.
- People who are likely to be exposed to high levels of contamination or in spaces with little ventilation should wear masks (see link below for further information).
If a person is infected, the disease appears within one to five weeks. Initial symptoms resemble the flu, including fever, body aches, abdominal problems, but if hantavirus is involved this can progress to severe trouble breathing. Anyone who develops difficulty breathing and has recently been in an area contaminated by rodents should see a doctor immediately.
- Even where its incidence among mice is highest, hantavirus infects only a tiny proportion of people who come in contact with it. However, in the few people who develop hantavirus infection, it can be fatal in one-third of the cases, if left untreated.
- There is no specific cure but early treatment in an Intensive Care Unit reduces the risk of death.
Deer mice surveys for hantavirus were done in Alberta around a decade ago. Between 4% and 23% of mice were positive. There was no correlation between the number of mice and the number of human cases.
Hantavirus is not a new risk to public health, and there is no evidence that it is increasing or spreading. All that is new is our ability to recognize it and deal with it more effectively through early diagnosis and treatment.
- The virus has existed in North America for many years, but was only recognized for the first time in May of 1993, in New Mexico.
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