Hantavirus has probably caused people to get sick for years in the United States, but it was not recognized until recently. A 1993 outbreak of fatal respiratory illness on an Indian reservation in the Four Corners area (the border of Utah, Colorado, New Mexico, and Arizona) led epidemiologists to the discovery of hantavirus as the causative agent. Since that discovery, hantavirus disease has been reported in every western state, and in many eastern states. Hantavirus is carried by rodents, particularly deer mice, and is present in their urine and feces. The virus does not cause disease in the carrier animal. Humans are thought to become infected when they are exposed to contaminated dust from the nests or droppings of mice. The disease is not, however, passed between humans. Contaminated dust is often encountered when cleaning long-vacated dwellings, sheds, or other enclosed areas. The federal Centers for Disease Control and Prevention (CDC) reported that rodents carrying hantavirus have been found in at least twenty national parks and that it is possible that the virus is in all of the parks. Epidemiologists at the CDC suspect that campers and hikers may have a higher chance of contracting the disease than most people. This is due to the fact that they pitch tents on the forest floor and lay their sleeping bags down in musty cabins. So far, however, of the more than 100 cases that have been reported in the U.S., only two were directly linked to camping or hiking. Most people who are exposed have come into contact with rodent droppings in their own homes. The initial symptoms of hantavirus disease closely resemble influenza. The disease begins abruptly with fever, chills, muscle aches (myalgia), headache, nausea and vomiting, and malaise. A dry cough may be present. The fever may be higher in younger people than in older people. For a very short period, the infected person feels somewhat better, but this is followed within a day or two by an increased respiratory rate caused by a seepage of fluid into the lungs. The initial shortness of breath is subtle and the patient may be unaware of it, but progression is rapid. The patient ultimately develops respiratory failure. An effective treatment for hantavirus is not yet available. Even with intensive therapy, more than half of the diagnosed cases have been fatal.
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