Hantavirus

Hantavirus is a type of virus carried by rodents. There are many types of hantavirus infections that infect rodents, and a few that can infect humans as well.


Causes/associated factors
Serious hantavirus infections have been noted for some time in Asia and Europe. This potentially life-threatening illness primarily affects the kidneys.
In 1993, a serious respiratory illness due to a newly recognized type of hantavirus, the Sin Nombre hantavirus, was detected in the United States. That spring, heavy snow and rain helped revive plants and animals after a prolonged drought in the "four corners" area of the southwestern United States. With plenty to eat, the deer mice popu- lation in the area exploded. The increased mouse population led to a sudden outbreak of this serious respiratory illness, now called hantavirus pulmonary syndrome (HPS).

Further investigation determined the illness wasn't new. Tissue samples preserved from people with unexplained respiratory deaths many years ago showed that the virus was present in the United States as early as 1959. Navajo Indians had long before that recognized a similar disease and also associated it with rodents.

It has since been determined that the Sin Nombre hantavirus is responsible for most cases of HPS in the United States, but that other hantaviruses can also cause the infection. You may be exposed to hantavirus when you contact infected rodents through domestic, occupational or leisure activities. Hantavirus is spread mainly by deer mice and cotton rats, both common in rural and semirural areas throughout the United States. Hantavirus may also be found in rice rats and white-footed mice in the United States. The common house mouse hasn't been identified as a carrier of this virus. In the United States, hantavirus has been identified in rodents in at least 31 states.

Sixty percent of all people who've been diagnosed with hantavirus are between ages 20 and 39. The illness is rare in children under age 12.


Transmission
Hantavirus particles are found in the urine, feces and saliva of infected rodents. These particles can get into the air when rodent nests or droppings are disturbed (by sweeping, for example). This process is called aerosolization. Humans are thought to contract hantavirus by breathing air contaminated with these viral particles. Less commonly, the virus may spread through the bite of an infected rodent, by eating contaminated food or by touching an object contaminated with rodent droppings or saliva and then touching your nose or mouth. Person-to-person spread hasn't occurred in the United States, but a few cases have occurred in South America.
Contamination is thought to be most probable inside rodent-infested homes, crawl spaces, garages, barns, storage facilities, shelters or other closed buildings that lack good ventilation. Brief exposure to such an environment may be all it takes to develop a hantavirus infection.

The incubation period (time from exposure until symptoms appear) for humans is about two weeks, but may range from a few days to six weeks.


Signs/symptoms
HPS primarily affects the blood vessels of the lungs, causing changes that allow blood to leak into the surrounding lung tissue. Initial symptoms may resemble the flu, often including fever, muscle aches and fatigue. You may also notice headaches, intestinal problems (such as nausea, vomiting, diarrhea and abdominal pain), dizziness and chills. About two to 15 days after symptoms appear, there's an abrupt change in symptoms as the lungs fill with fluid. In some cases, cough and shortness of breath may progress rapidly to respiratory failure and shock.

Diagnosis
Diagnosis is based on your medical history (especially possible exposure to hantavirus), current symptoms and a physical exam. Blood tests to check for specific antibodies can confirm the diagnosis.

Treatment
If you have HPS, you must be closely monitored in an intensive care unit. Treatment is supportive, focusing on preventing shock and maintaining heart and lung status. The doctor will make sure your heart rate and blood pressure remain stable and your blood has enough oxygen. It often takes about a week after the severe respiratory symptoms appear to recover. These symptoms often subside as quickly as they appeared. Complete recovery may take weeks or months, however.

Complications
Despite intensive care, more than one-third of all people who develop HPS don't survive. Those who do survive usually recover completely, but a few have lasting respiratory problems.

Pregnancy-specific information
Due to the recent identification of this illness, the full effect of HPS during pregnancy isn't known. Based on the few cases that have been observed in pregnant women, the infection doesn't appear to spread to the developing baby.

Senior-specific information
Growing older isn't a risk factor for HPS.

Prevention
To prevent HPS, the Centers for Disease Control and Prevention (CDC) recommends the following rule of thumb: air out, seal up, trap up and clean up. Here are some specific suggestions to help you keep rodents out of your home:
If you have a wooden, earthen or adobe home, create a rodent barrier by placing metal roof flashing around the base of the house. The barrier should run 6 inches underground and 12 inches above ground.

Discourage rodent burrowing by placing 3 inches of gravel under the base of your home, including mobile homes. Cover any openings into your home ¼ inch or larger with steel wool or cement. Use tight-fitting screens on all doors and windows that are left open.

Use raised cement foundations when building sheds, barns or outbuildings.

Keep the grass mowed and eliminate rodent shelters, food sources and woodpiles within 100 feet of your home. Elevate woodpiles at least 12 inches, and don't let debris accumulate.

Store food, pet food, grain and garbage in covered, rodent-proof containers. Don't leave pet food in outdoor dishes.

Avoid placing birdfeeders near your home. If you do have birdfeeders, choose the "squirrel proof" variety and clean up any spilled seed every evening.

Wash dishes and clean up spilled food promptly. Clear up any clutter.

Eliminate rodent access to water. Repair leaks and moisture problems, insulate water pipes to prevent condensation, and make sure rodents can't get to water sources such as aquariums, cleaning equipment and flowerpots.

Place spring-loaded rodent traps within 100 feet of your home, as well as inside. A pea-sized amount of chunky peanut butter can be used as bait.
Tips for cleanup projects


Ventilate closed buildings for at least 30 minutes before beginning work.

When cleaning areas with large numbers of rodents, wear coveralls (disposable if possible); rubber boots; rubber, latex, vinyl or nitrile gloves; protective goggles; and a respiratory protection device with a filter mask. Contact your local health department for tips on disposal methods.

Wear rubber, latex, vinyl or nitrile gloves when cleaning rodent-infested areas and disposing of dead rodents. Before removing the gloves, wash your gloved hands in a household disinfectant and then in soap and water. Thoroughly wash your hands with soap and water after taking off the gloves.

To deactivate the virus and prevent aerosolization, soak all rodent-contaminated areas with a general purpose disinfectant for five minutes. (A solution of 1 1/2 cups of liquid bleach in 1 gallon of water, prepared on the day of use, is effective.)

Don't sweep or use a vacuum. Pick up wet rodent droppings, food piles and nests with a paper towel and then mop the area with disinfectant. Be sure to properly dispose of all towels, droppings, food and nests in the garbage.

If you suspect HPS within 45 days of possible exposure, seek medical attention immediately.
If your work includes handling or exposure to wild rodents, discuss your risk and precautions with your employer.