Since October is the American Lung Associations "Healthy Lung Month" PersonalMD.com is pleased to bring you the first of a number of articles this month that will highlight the importance of maintaining healthy lungs. Thomas E. Booth, MD, MS VP, Medical Affairs PersonalMD.com

An outbreak of severe lung infections in the southwest U.S. during the summer of 1993 led to the identification of hantavirus as the cause. Prior to this, hantavirus had mainly been seen in Asia and Europe. Though there have only been about 100 cases of hantavirus infection reported in the U.S. since s 1993, this is a serious disease that can be rapidly fatal.

Hantavirus is a member of the viral family known as Bunyaviridae. This family includes several rare but serious viruses including the California encephalitis viruses, which cause an infection of the brain (known as encephalitis). Encephalitis usually affects children and can cause seizures, permanent brain damage and death.

Hantavirus, however, has its most severe effect on the lungs. After the outbreak in 1993, the infection caused by hantavirus became known as the hantavirus pulmonary syndrome. The beginning of the syndrome can easily be mistaken for the flu and is very non-specific. Fever, chills, muscle soreness, headache, cough, nausea, vomiting, malaise ("feeling lousy"), diarrhea, dizziness and joint pain or soreness can all be present to varying degrees. When a patient comes to a doctor and mentions these symptoms, hantavirus infection is probably one of the last things on the physicians mind.

After roughly two to five days of flu-like symptoms, however, things take a turn for the worse. A rapidly developing shortness of breath occurs at this time and is generally severe. This is unusual in common viral respiratory infections, such as influenza (the virus that causes the flu). The shortness of breath often becomes severe enough to require supplemental oxygen to be administered.

antibody

any of a large number of proteins of high molecular weight that are produced normally by specialized B cells after stimulation by an antigen and act specifically against the antigen in an immune response, that are produced abnormally by some cancer cells, and that typically consist of four subunits including two heavy chains and two light chains

carrier

a person, animal, or plant that harbors and disseminates the specific agent (as a microorganism) causing an infectious disease from which it has recovered or to which it is immune

encephalitis

inflammation of the brain

Shock frequently occurs in hantavirus infection, which can include low blood pressure, low oxygen in the blood and decreased heart function. Intravenous fluids and medications may be required to help maintain the blood pressure. It is also not unusual for people to require intubation (a breathing tube placed through the mouth and into the windpipe) and a breathing machine temporarily to survive. Kidney failure can also occur in severe cases.

Unfortunately, no medications or antibiotics are available to directly attack the hantavirus and treatment is generally supportive. Even in the face of good medical management, hantavirus infection is fatal in roughly 40 percent of cases, usually due to lung failure. The good news is that those who survive the first 48 to 72 hours of the illness generally get better rapidly and have no residual problems from the infection.

Thus, while research into medicines which treat hantavirus directly is ongoing, most current efforts are being focused on prevention of the disease. Hantavirus appears to reside in rodents and these infected rodents seem to be the reservoir (or carrier) for the disease.

The deer mouse was thought to be responsible for the outbreak in 1993. The people infected during this outbreak lived in the same area as the deer mouse and due to favorable weather conditions, the deer mouse population was at a peak that summer. Thus, many people were exposed to the infected deer mice. Other rodents are thought to be responsible for cases elsewhere in the United States.

epidemic

affecting or tending to affect an atypically large number of individuals within a population, community, or region at the same time

pulmonary

relating to, functioning like, associated with, or carried on by the lungs

seizures

a sudden attack (as of disease)

transmission

an act, process, or instance of transmitting

Persons who live in a dwelling in a rural area which is permeable to rodents or who have an occupational exposure to rodents have a higher chance of becoming infected with the hantavirus. Avoidance of rodent exposure virtually eliminates the possibility of hantavirus infection. While person to person transmission of hantavirus is not thought to occur, isolation of affected individuals may be undertaken due to the illness not yet being diagnosed at the time of initial patient presentation.

Diagnosis of hantavirus exposure can be made via a blood test which detects antibodies the body has made against the hantavirus. This is a highly accurate test in most persons infected. Unfortunately, knowing the diagnosis often helps little in determining outcome. The only exception would be in the face of an epidemic, when supportive measures can be started before severe symptoms develop.

The hantavirus pulmonary syndrome is a rare, but frequently fatal disease caused by infection with the hantavirus. The disease is not known to occur in the absence of exposure to rodents and person to person transmission is not thought to occur. Hopefully, scientific research will allow us to learn enough about this deadly virus to one day find a cure.