Hantavirus Pulmonary Syndrome: How To Protect Yourself
The recent cases of a rare life-threatening respiratory disease among people who visited Yosemite National Park earlier this summer have raised concerns about how the disease is contracted and how it can be prevented and treated.
So far, the National Park Service has announced that there have been three confirmed cases and an additional probable case of hantavirus pulmonary syndrome (HPS). Two people have died, including a man from Alameda County. All four people stayed in tent cabins in Curry Village at the eastern end of Yosemite Valley in mid-June.
"Hantavirus pulmonary syndrome is a very rare disease caused by a group of viruses, called hantaviruses, that are carried by rodents such as mice and rats," says infectious disease specialist Dr. Dianne Martin, who co-chairs the Infection Control team at Washington Hospital. As of July 3, the Centers for Disease Control and Prevention (CDC) had recorded a total of only 602 cases of HPS nationwide since the disease was first identified in 1993. A total of 50 cases had been reported in California prior to the recent announcements.
"There is absolutely no evidence to date that you can catch HPS from another person or from a blood transfusion," she emphasizes. "The virus is spread to humans through exposure to rodent saliva, urine or feces droppings. Typically, that exposure happens when people breathe in air that is contaminated by the virus. For example, when someone sweeps up rodent droppings or nesting materials, tiny particles containing the virus get into the air.
"It also may be possible for people to get the virus if they touch something that has been contaminated and then touch their nose or mouth," she adds. "There was one case here in California about 10 years ago where it appears to have been caused by food that may have been contaminated. Exposure to the virus through a bite by an infected rodent is considered extremely rare."
There are several different strains of hantavirus. In California, the rodents that may carry hantavirus are deer mice. According to the CDC, the strain of hantavirus that may be present in some deer mice is called Sin Nombre. Deer mice can be found throughout the country. In regions outside California, different strains of hantavirus that can cause HPS may be carried by rice rats in the southeastern U.S.; by white-footed mice in southern New England, the Mid-Atlantic states, southern states, mid-western and western states, and Mexico; and by cotton rats in the southeastern U.S. and in Central and South America.
The CDC cautions that other rodents may carry strains of hantavirus that cause HPS, but they have not yet been identified. In addition, other rodents may carry hantaviruses that cause a different infection called hemorrhagic fever with renal syndrome (HFRS). The CDC therefore advises people to avoid close contact with wild rodents in general.
"If you are traveling outside the U.S., it's important to note that there are more hantaviruses in South America and Korea than there are in North America," Dr. Martin says. "Because HPS has an incubation period of anywhere between one and six weeks, you might not have any symptoms until you get home."
Symptoms, Complications and Treatment of HPS
"Diagnosing HPS is difficult because the early symptoms are very non-specific and mimic those of other diseases such as the flu," Dr. Martin notes. "The hantavirus works its way into the lining of the lungs, creating inflammation. People may experience a fever, fatigue and muscle aches, especially in the thighs, hips, back and shoulders. In some cases, early symptoms also might include headaches, chills, dizziness, nausea, diarrhea or vomiting. HPS rarely causes a runny nose, sore throat or rash.
"As the disease progresses, it can create serious respiratory problems," she continues. "The person is likely to develop a chronic cough, shortness of breath and an intense sense of pressure in the chest. Even though these could be symptoms of the flu, too, anyone who is experiencing these symptoms and has had a possible exposure to rural rodents should call a doctor right away and explain that potential exposure."
The CDC reports that many individuals who contract HPS recover completely, with no chronic infection or lasting effects. The mortality rate of 38 percent, however, is considerably higher than for influenza.
"There are no vaccines to immunize people against hantaviruses, and there is no simple cure for HPS," Dr. Martin says. "Because it is a viral disease, it can't be treated with antibiotics, which work only against bacterial infections."
Patients who are suspected of having HPS may need to be hospitalized and receive medical care in an intensive care unit. The earlier a patient is treated, the better the chances for recovery.
"Treatment is essentially the same as for the flu, with bed rest and plenty of fluids," explains Dr. Martin. "Acetaminophen may be used to control fever and pain. Other medications may be administered if the patient is experiencing low blood pressure. In some serious cases in the ICU setting, a surgeon may perform a procedure called 'extracorporeal oxygenation,' inserting a tube into the patient's body and using an oxygen pump to increase the oxygen levels in the body."
Preventing Hantavirus Exposure
Anyone who comes in contact with rodents is at risk for exposure to hantavirus, according to the CDC.
"Wild rodents tend to be more prevalent in rural areas, so people who live, work and vacation in rural areas and the outdoors may be at a greater risk for hantavirus exposure," Dr. Martin suggests. "Obviously, as the cases in Yosemite have shown, campers and hikers in national and state parks may be at risk, too. However, a substantial number of HPS patients have been people who were exposed to the virus due to infestations of infected rodents in their own homes or in nearby barns or storage areas."
Dr. Martin offers several suggestions for limiting your potential for exposure to hantavirus:
- Keep rodents out of your home by sealing holes or gaps inside and outside the house where they can enter, such as under cabinets, around pipes, in basements and attics, around the foundation or around doors and windows.
- Consider using traps or bait if you have a serious infestation of rodents, making sure you always carefully follow the instructions provided and dispose of all materials properly.
- When cleaning up rodent urine or droppings, wear rubber gloves and spray the area with a strong disinfectant or bleach solution and let it soak for several minutes before wiping up with paper towels. Then mop or sponge the area again with a disinfectant or bleach solution. Wash your gloved hands thoroughly before taking off the gloves, and wash your hands again after you take off the gloves. Dispose of all paper towels, mop heads and gloves in plastic bags and place them in covered trashcans.
- About 20 percent of mice/rodents carry the disease and are usually asymptomatic, so one cannot tell that a rodent is carrying the disease and people should avoid touching the animals - dead or alive.
"Above all, do not sweep up rodent droppings, urine or nests with a broom or vacuum cleaner," she emphasizes. "That would cause the virus particles to get into the air you are breathing.
"I also want to stress that HPS is exceedingly rare," she adds. "I might see just one case in my lifetime. You are so much more likely to get the flu - so be sure you get your flu shot. That's one disease we really can help prevent!"
Yosemite National Park has a non-emergency phone line open from 9 a.m. to 5 p.m. daily to answer questions and concerns related to hantavirus exposure in the park: 209-372-0822. The CDC also has a hotline number: 404-639-1510. Additional information about hantaviruses and HPS also is available at the CDC Web site at www.cdc.gov/hantavirus/ The Web site also offers a booklet, "Facts About Hantaviruses." that is available for downloading and contains additional suggestions for avoiding exposure to hantaviruses.