Hantavirus Pulmonary Syndrome (HPS) is a potentially fatal viral infection carried principally by deer mice, but also found in other rodents. There have been over 322 known cases of HPS in the United States as of June 2002 with almost 40 percent resulting in death. However, the survival rate is greatly improved when proper diagnosis and medical support are rapidly obtained. The disease is relatively difficult to get and easy to avoid by taking the necessary precautions. In California, many hantavirus cases have occurred in the central Sierra Nevada.