Hantavirus Pulmonary Syndrome

Hantavirus Pulmonary Syndrome

Also called: New York 1 Virus Infection, Hantavirus, HPS, Sin Nombre Virus Infection

Reviewed By:
Vikram Tarugu, M.D., AGA, ACG

Summary

Hantavirus pulmonary syndrome (HPS) is a rare but often fatal respiratory disease that people contract from exposure to HPS-infected rodents such as certain types of mice and rats. HPS was first identified in the southwestern United States in the spring of 1993. While HPS is very rare in the United States, it does have a particularly high fatality rate.

People contract HPS when urine, fecal droppings or saliva of infected animals is stirred up and tiny droplets of the HPS virus (hantavirus) become airborne. Materials in a rodent’s nest may contain the virus, which can then be transferred to people who touch the nest before touching their eyes, nose or mouth. A bite from an infected rodent also can transmit a hantavirus.

Symptoms of HPS typically appear one to five weeks after exposure to a hantavirus. Initial symptoms often include fever (which is usually higher in younger people), fatigue and severe muscle aches. HPS quickly progresses to a condition known as adult respiratory distress syndrome (ARDS), in which the lungs fail to adequately transfer oxygen to the blood. This compromises the function of all the body’s organs and often results in death.

In diagnosing HPS, a physician will look for signs of ARDS and will note any decrease in blood pressure (hypotension) or decrease of oxygen levels in the blood (hypoxia). Blood tests also may be performed to look for elevated levels of white blood cells, decreasing platelet counts and other indicators of HPS.

There is no specific treatment for HPS, and a vaccine is not available, although research is ongoing to develop a vaccine. Patients are often admitted to an intensive care unit, where they are given oxygen therapy to help ease them through the period of severe respiratory distress associated with the illness.

To prevent HPS, people are urged to avoid contact with all wild rodents, including squirrels and chipmunks. In addition, it is important to clean up all rodent urine and fecal matter. When cleaning, sweeping or vacuuming should be avoided. These activities may can raise dust and send hantavirus particles into the air – increasing the risk of infection if the virus is inhaled.

All rodent nests should be cleared from the home. Gloves should be worn during the cleaning process, and hands should be thoroughly washed immediately afterwards. Several steps can be taken to keep mice and rats out of the home, including sealing food items and cleaning up after meals, sealing holes on the exterior and interior of the house and removing trash, brush and weeds from outside the home.

About hantavirus pulmonary syndrome

Hantavirus pulmonary syndrome (HPS) is a rare but potentially life-threatening respiratory disease that people contract from exposure to rodents, especially certain types of mice and rats. In North America, deer mice are most often responsible for transmission of HPS. Other animals known to transmit this illness include white-footed mice, rice rats and cotton rats. It is possible that squirrels and chipmunks may also carry the HPS virus.

HPS first was diagnosed in the southwestern United States in the spring of 1993. It results from exposure to a group of viruses known as hantaviruses, which were first identified internationally in 1978. The four hantaviruses known to cause HPS are:

  • Bayou hantavirus
  • Black creek canal hantavirus
  • New York hantavirus
  • Sin nombre hantavirus

People contract HPS when urine, fecal droppings or saliva of infected rodents are stirred up and tiny droplets of the virus become airborne. This process is known as aerosolization. People become infected after breathing in this airborne virus.

Materials in rodent’s nests may contain hantaviruses, which can then be transferred to people who touch the material before they touch their eyes, nose or mouth. A bite from an infected rodent can also transmit a hantavirus. Experts suspect that some people become sick when eating food contaminated with rodent urine, droppings or saliva that contain the virus.

There has never been a documented case of person-to-person transmission of a hantavirus in the United States. Therefore, people do not have to worry about contracting the virus after kissing, touching or having other intimate contact with someone who is infected. The virus also cannot be transmitted during blood transfusions.

Hantaviruses typically remain viable in a room-temperature environment for two or three days. Ultraviolet rays from the sun can kill hantaviruses. On the other hand, freezing temperatures may actually increase the time a hantavirus remains viable.

Hantaviruses are contained within a fatty substance. This substance can be destroyed by solutions that dissolve fat, such as bleach, alcohol and disinfectants – effectively killing the virus. For this reason, people are advised to clean areas that may have been exposed to infected rodents using a bleach solution or a disinfectant.

HPS is rare in the United States. Nonetheless, it has occurred in all areas of the country except Alaska and Hawaii. The majority of cases appear in the southwest during the spring and summer. As of September 2006, the last date for which statistics are available, 453 cases of HPS have been reported in the United States, according to the U.S. Centers for Disease Control and Prevention. The disease has a high mortality rate and has resulted in death for 35 percent of patients diagnosed with HPS.

Activities that increase the risk of exposure to hantaviruses include:

  • Housecleaning. Sweeping and vacuuming areas frequented by infected rodents can send particles into the air that may expose a person to hantaviruses.

  • Certain types of work. Construction, utility and pest-control workers may be exposed to hantaviruses when working in crawl spaces, under houses or in vacant buildings.

  • Campers and hikers. People may be exposed to hantaviruses in trail shelters that are infested with rodents. Camping in rodent-infested habitats can also make people vulnerable to hantavirus infection. The viruses are known to be present in at least 20 national parks in the United States.

Rodents that carry hantaviruses do not become sick from the infection. Certain types of mice and rats have never been known to transmit hantaviruses to humans. These include house mice, roof rats and Norway rats. Common household pets such as dogs, cats, guinea pigs, hamsters, gerbils or other rodents from pet stores also do not transmit hantavirus infections.

Signs and symptoms of HPS

Symptoms of hantavirus pulmonary syndrome (HPS) typically appear between one to five weeks after exposure to a hantavirus. Initial symptoms often include fever (which is often high in young people), fatigue and severe muscle aches, particularly in the thighs, hips, back and shoulders. Other symptoms include:

  • Abdominal pain
  • Chills
  • Diarrhea
  • Dizziness
  • Headaches
  • Nausea
  • Stomach pain
  • Vomiting

Four to 10 days after the initial symptoms appear, patients may begin to experience the next wave of symptoms. These include coughing and shortness of breath as the lungs fill with fluid. HPS can quickly progress to a condition known as adult respiratory distress syndrome (ARDS), in which the lungs fail to adequately transfer oxygen to the blood. This compromises the function of all the body’s organs and results in death for 30 to 40 percent of patients who have the condition.

Diagnosis and treatment methods for HPS

In diagnosing hantavirus pulmonary syndrome (HPS), a physician will perform a complete physical examination and compile a thorough medical history. The physician will look for signs of adult respiratory distress syndrome (ARDS) and will note any decrease in blood pressure (hypotension) or decrease in the levels of oxygen in the blood (hypoxia).

Blood tests also may be performed to look for elevated levels of white blood cells, decreasing platelet counts, the presence of certain antibodies and other indicators of HPS. A chest x-ray may be ordered to look for lung problems that may be associated with HPS.

There is no specific treatment for HPS, and a vaccine is not available, although research is ongoing to develop a vaccine and discover effective medications. Patients are often admitted to an intensive care unit, where they are given oxygen therapy to help ease them through the period of severe respiratory distress known as ARDS. Assisted respiration with a ventilator is the main treatment for ARDS. The earlier during the illness a patient is admitted, the better the prognosis – especially if hospitalization occurs prior to the onset of ARDS.

Prevention methods for HPS

To prevent hantavirus pulmonary syndrome (HPS), people are urged to avoid all wild rodents, especially mice and rats. In addition, it is important to clean up all rodent urine and fecal matter. When cleaning, it is important to avoid sweeping or vacuuming, which can raise dust, stir up HPS virus particles and make them airborne. If these particles are then inhaled, a person can become infected.

People are urged to use gloves during cleanup and to pour disinfectant or bleach mixed with water onto the rodent waste and affected area, and then wait five minutes before beginning to clean the area. Wet, sturdy paper towels or disposable rags should be used to remove and dispose of the droppings. The affected area should be cleaned a second time with the disinfectant or bleach solution. Sweeping and vacuuming such waste is not advised. After cleaning, hands should be thoroughly washed.

Rodent nests and nesting materials also should be cleared from the home. People should not handle these materials unless they are wearing gloves, and the nest remains should be placed in a sealed bag and disposed of according to state health department recommendations. Any rodents caught in traps should be sprayed with disinfectant, and the traps should be disinfected again after the rodent has been removed. In addition, people in the western United States may be at risk for contracting plague from the fleas of dead rodents. As a result, people are urged to wear insect repellent when picking up dead rodents.

Hantavirus transmission can occur when cleaning out cabins, sheds, barns and other similar buildings that have been closed for a period of time. When cleaning these structures, it is best to open all doors and windows and to leave the area for 30 minutes prior to cleaning. People are urged to wear rubber or plastic gloves and to spray disinfectant on all surfaces before beginning the cleaning process. Upholstered furniture should be steam-cleaned, shampooed or sprayed. All bedding and clothing should be washed using detergent and hot water.

Items that a person cannot clean should be discarded. This may include papers, books and other delicate items. In some cases, these items can be left outside in sunlight for several hours or inside in sunlight for at least a week to allow ultraviolet rays to kill the virus.

Several steps can be taken to keep wild rodents out of the home, including:

  • Keep food in plastic or metal containers with tight lids. Also, place garbage (both indoors and outside) in plastic or metal containers with tight lids.

  • Clean up spilled food immediately, and promptly wash dishes and utensils after eating.

  • Do not leave food in a pet’s bowl overnight.

  • Check the inside of the house for gaps or holes that a pencil can fit into and fill with steel wool, lath metal or caulk. Common entry areas for rodents include kitchen cabinets, closets, doors, air vents and sinks. Seal outside holes and gaps with cement, lath metal, hardware cloth or sheet metal. Outside entry points for rodents include any holes, windows and doors, and around electrical, plumbing or gas lines.

  • Use snap traps to catch mice or rats. Glue traps and live traps are not recommended, because these traps may scare the rodent and cause it to urinate. This can increase the risk of being exposed to hantavirus.

  • Do not allow trash, brush or weeds to build up outside the home, particularly around the foundation in order to avoid attracting rodents.

Questions for your doctor regarding HPS

Preparing questions in advance can help patients to have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions related to hantavirus pulmonary syndrome (HPS):

  1. How can I tell if I have HPS?

  2. What are the signs that my condition has progressed to adult respiratory distress syndrome (ARDS)?

  3. How will you diagnose HPS?

  4. Will I require hospitalization for my condition?

  5. What are my treatment options?

  6. What are the side effects of these treatments?

  7. What changes in my condition should I report to you?

  8. Is there anything I can do to prevent contraction or spread of HPS?

  9. What resources offer advice for safely cleaning areas that may contain the HPS viruses?

  10. What medications are being tested to treat HPS?
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