The hantavirus pulmonary syndrome—formerly Korean hemorrahgic fever—is a rare but often fatal disease. The symptoms seem like influenza mixed with gastrointestinal problems: "fever, chills, sweaty palms, diarrhea, malaise, headaches, nausea, abdominal and back pain, respiratory problems such as the ones." These start "three to seven days and arise about two to three weeks after exposure." After that, a phase that includes tachycardia (abnormally rapid heart rate) and tachypnea (abnormally rapid breathing). Then patients "will develop difficulty breathing, coughing and shortness of breath." At this point, the patient could enter into the "cardiopulmonary phase, where cardiovascular shock can occur, and hospitalization of the patient is required."
source : http://gizmodo.com/5939013/unprecedented-deadly-virus-outbreak-in-california