Hantavirus and Mice: Symptoms, Treatment, and Prevention

Hantavirus is a disease carried by a variety of small rodents and passed to humans through urine, feces, and saliva.

Though it is passively borne by the mice and rats who carry it, and though human infection is relatively rare, once humans become infected it can turn into Hantavirus Pulmonary Syndrome (HPS) which, sadly, is often fatal.

How can people become infected with Hantavirus?

At home or on the job, Hantavirus is most often transmitted to people when they stir up dried mouse droppings or nests by sweeping.

The Washington Post notes that infection is most likely to occur “in houses, garages, and cabins, especially while cleaning.” People who work in occupations where they are regularly exposed to mouse and rat nests, or who are going to be in a place where mice often make their nests (think everything from people who clean crawlspaces to campers staying in a cabin in a National Park) should take particular caution.

In an effort to protect their members, the International Association of Certified Home Inspectors (InterNACHI), “believes that crawlspaces are the most likely locations that the Hantavirus may be encountered” and also notes that extreme care should be taken in foreclosures or other homes that have not been occupied for long periods of time.

Do all mice carry Hantavirus?

If you were recently exposed to rodent droppings or saliva, there’s no need to panic. While there is a very large number of mouse species that call America home, there are only four known carriers of Hantavirus. According to the CDC, these are:

  • The cotton rat (found in the southeast US);
  • The deer mouse (found throughout the majority of North America);
  • The rice rat (also found in the southeast, but semi-aquatic and prefers marshy areas);
  • The white-footed mouse (found in southern New England, mid-Atlantic, and the Midwest).

That shortlist leaves quite a wide range of mice that a person may come into contact with which do not carry Hantavirus.

Hantavirus has only been documented in the US since an outbreak in the Southwest in 1993. Since then, there have been more than 600 documented cases of HPS, just under half of which were fatal.

In a survey of twenty years’ reporting to the CDC, Knust and Rollin (2013) noted that there were some instances of milder infections that didn’t present as full-blown cases of HPS and thus weren’t counted. They also documented that another form of Hantavirus, Seoul virus, has been found in black and Norway rats here (it’s known as an “old world” virus and is found throughout Asia and Europe), but it hasn’t been transmitted to people.

Symptoms of Hantavirus

One of the trickier aspects of the disease is that when people first get sick it usually seems like they just have the flu. Of course, it’s good that there haven’t been that many cases of HPS, but it does mean that doctors aren’t sure how long it takes for the virus to incubate.

Generally, the CDC says it takes from 1 to 8 weeks from exposure for symptoms to develop. The CDC outlines the specific Hantavirus symptoms, differentiating between early and late-onset ones. People who have just gotten sick will all feel tired, have muscle aches in their large muscles (think thighs and back), and have a fever. Some will also have a headache, chills, tummy troubles, and might feel dizzy. Anywhere from 4 to10 days with these early symptoms is the lead-in to the potentially fatal late-stage symptoms of coughing and shortness of breath which indicate that the patients’ lungs are filling with fluid.

For a bit of bad news swirled in with some good news, some cases of Hantavirus confirmed by the lab didn’t present with the expected pulmonary symptoms and were generally more mild infections. Without the pulmonary element, they weren’t reported to the CDC, so it’s possible that Hantavirus infection rates are actually higher than currently believed, though the uncounted incidences were not as deadly. Knust and Rollin advise changing the definition so all lab-confirmed diagnoses will be counted by the CDC.

How to treat Hantavirus?

Hantavirus treatment is inexact because there’s no regimen or cure specifically for HPS, only management of the symptoms.

If you believe you’ve come in contact with rodent debris and then come down with flu-like symptoms, make sure you mention it to your doctor so they can run the proper tests for rodent-related diseases.

Once HPS is confirmed, the CDC protocol for treatment recommends that patients be placed in intensive care to receive oxygen therapy. Unfortunately, 38% of all cases of HPS have been fatal, but early intervention makes a huge difference.

Steps to prevent Hantavirus

The best news about Hantavirus transmission is that in the United States there have been no cases where a person contracted the virus from another person.

Hantavirus mice are the “rodent reservoir” for the disease and by avoiding contact with rodents, their nests, and their droppings people can be reasonably confident that they will be safe from contracting the disease.

Some people did report to their doctors that they didn’t have any contact with mice before they got sick, so it’s still important to not be complacent if you come down with any of the symptoms the CDC describes.

If you live or are planning a camping trip or other activities in an area that is home to one or more of the known carrier animals, your best defense against contracting Hantavirus is to avoid disturbing them!

If you’re cleaning out a cabin, crawlspace, or garage and come across a mouse nest definitely don’t sweep up the nest or any droppings you find without putting on protective gear and learning how to properly do it.

For Hantavirus prevention, the CDC recommends donning a protective respirator, gloves, and goggles, spraying any old mouse house or mess with a diluted bleach solution, and letting it thoroughly saturate before wiping up the mess with paper towels.

Who is most at risk of contracting?

The Canadian Centre for Occupational Health and Safety (CCOHS) provides a concise list of the activities commonly reported in people in the US and Canada who have been diagnosed with HPS. The activities range from cleaning outbuildings on a farm or a ranch to finding mice for study in a lab, to simply entering a barn that has a lot of mice in it, to walking through areas with lots of rodents while out hiking or camping.

There is a slightly higher incidence of men contracting the disease than women. The CDC chalks that up to possibly being linked to the types of jobs they do that would heighten their chances of exposure.

Hantavirus FAQ

How long does Hantavirus live in rodent droppings?

Dr. Charles Chiu at the University of California San Francisco notes that after the carrier mice have been eliminated from the area, the virus does not survive for very long in the dust.

WebMD also points out that the CDC guideline is that after a week any virus from eradicated mice would no longer be contagious to humans, but cautions that any nests that seem long-abandoned should still be approached with caution and never swept up, creating dust.

How common is Hantavirus in mice?

Sometimes called “deer mice disease,” Hantavirus is only confirmed to be carried in the US by four species of mice and rats.

Medline Plus notes that it does not make the animals themselves sick, and Health Canada noted that they tested a large number of deer mice in Northern Ontario and found the virus only in a small percentage.

Do all mice carry Hantavirus?

No! The CDC has confirmed only four species of mice and rats that carry the various strains of HPS-causing Hantavirus in the US. These species are the cotton rat, the rice rat, the deer mouse, and the white-footed mouse.

There have been a few confirmed cases of “old-world” Hantaviruses carried by black rats and Norway rats, but that is just in the rats, not communicated to people.

2 Comments

Jim Marshall

This is a question. It was kind of answered in the above Health Canada mention from Northern Ontario but is there a known percentage of Deer Mice that carry Hantivirus. Example of ball park figures: 5, 10, 20, 30 %. I realize there is no exact number but wondering if there is an “Around about figure??” Also if a rug laying on the floor but not disturbed had droppings in it & someone sniffed the rug could that be dangerous?? Thank you!!

    InsectCop

    Some sources say that around 15 to 20% of them are infected, we can’t comment on how precise these numbers are, though. As for sniffing the rug, it can be potentially dangerous, assuming the droppings came from an infected mouse, and the virus was still alive when it got inhaled. Checking in with the doctor would be advised, especially, if any symptoms occur.

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