What is hantavirus?
In 1993, a new medical mystery surfaced in the Four Corners area of the U.S. Southwest. It started when a young Navajo couple died within a few days of each other. Each had seemed perfectly healthy until a sudden illness left them gasping for breath. In each case, death came rapidly. Tests showed that they didn't have bubonic plague or any other known disease. After checking records of other local deaths, health officials found the same pattern repeated several times over: Healthy, young adults were mysteriously dying within days of catching an unknown disease that attacked their lungs with remarkable speed.
Studying tissue samples taken from the victims, researchers at the Centers for Disease Control and Prevention were able to pinpoint the culprit, a previously unknown type of hantavirus. Scientists already knew that hantaviruses were carried by mice and other rodents. It now seemed likely that rodents in the Southwest were spreading a deadly viral illness to humans.
Once they knew what they were looking for, scientists discovered that hantavirus in humans wasn't as new as they thought. They found traces of the germ in the remains of a 38-year-old Utah man who died in 1959. The disease was even known in Navajo medical tradition, down to its association with mice, and native people had developed the same prevention strategies that public health officials were advising.
By December 2009, there were a total of 534 confirmed cases of hantavirus illness in the United States. They occurred mostly in the western half of the country (especially the Southwest), though cases have shown up in 30 different states, including a few eastern states. Thirty-six percent of known patients has died from the infection.
How do people catch hantavirus?
People catch the germ from deer mice, cotton rats, and other rodents. Infected rodents don't get sick, but they do shed germs in their feces, urine, and saliva. Most often, people get sick by breathing in air contaminated by the virus. When lots of mice gather in a small space -- such as a woodshed or a garage -- the germs can become airborne. Mice have a habit of stirring up nesting material, sending all sorts of things skyward, and humans can further contaminate the air by sweeping germ-ridden floors.
A few people have caught hantavirus after being bitten by a rodent. It might also be possible to catch the germ by touching your nose or mouth after handling something contaminated with rodent urine or droppings. According to the CDC, it doesn't seem likely that the disease can spread from one person to another.
What are the symptoms?
The illness caused by hantavirus is called hantavirus pulmonary syndrome, or HPS. Most cases are caused by the Sin Nombre (Spanish for "nameless") hantavirus, though there are several other hantaviruses that can also cause HPS.
At first, HPS feels a lot like a bad case of flu, complete with fever, chills, and muscle aches. Other symptoms may include headache, nausea, vomiting, abdominal pain, diarrhea, and fatigue.
After about three to four days, the illness rapidly worsens. Victims suddenly have trouble getting enough air into their infected lungs, leaving them coughing and fighting for breath. Within 24 hours of the first signs of breathing trouble, they may need a ventilator to stay alive. For now, there's not much else doctors can do to treat the disease.
How can I avoid catching hantavirus?
Although hantavirus infections are vary rare, it makes sense to be careful around rodents and the places they nest, especially if you live in the Southwest or another area where hantavirus has already been reported.
If you know that you have mice in your house, shed, garage, or workplace, try to get them under control. For starters, check to see how they're getting in, and if possible seal off potential entryways. Keep in mind that a mouse can climb through a hole only slightly bigger than an inch wide. A few well-placed traps can keep the population down, too. You can discourage them further by keeping your house clean and making sure no food is left out in the open. If you catch a mouse in a trap, put on cleaning gloves, spray it with a disinfectant and double-bag it before throwing it away (or, even better, burying it).
If you discover a room with obvious rodent droppings, clean with caution. Don't just start sweeping up or vacuuming; there's too much risk of stirring up germs. Instead, put on a pair of gloves and wet down the mess with a commercial disinfectant or diluted bleach. After everything is wet, wipe the area with a cloth and mop or sponge it with disinfectant again. Spray your gloves with disinfectant before taking them off. Double-bag the cloth, gloves and other used cleaning materials before putting them in the trash.
You should also be rodent-wise in the great outdoors. Don't disturb rodent burrows, and don't set up a tent or sleeping bag next to woodpiles or other places that might be packed with mice. Store your food in rodent-proof containers, and don't touch or feed any rodents, even if they seem tame and friendly.
Most of the time, mice and other rodents are nothing more than a nuisance. But as long as hantavirus is around, you don't want to take any unnecessary risks.
Centers for Disease Control and Prevention. All about hantavirus. 2006.
American Lung Association. Hantavirus pulmonary syndrome fact sheet.
Graziano, K.L. and B. Tempest. Hantavirus pulmonary syndrome: A zebra worth knowing. American Family Physician. September 15, 2002.
California Department of Health Services. Facts about hantavirus in California.
Journal of the American Medical Association. Chagas patient page. Nov. 14, 2007.
Centers for Disease Control and Prevention. Case Information: Hantavirus Pulmonary Syndrome Case Count and Descriptive Statistics. December 2, 2009.