HPS was first reported in the United States in the spring of 1993. Cases were reported in Lincoln, Adams, Lewis, Yakima, Stevens, Grant, Franklin, Snohomish and King counties.
Symptoms develop in one to six weeks after exposure to aerosolized virus.
The first symptoms are fever, chills, muscle aches, and sometimes nausea, vomiting, and abdominal pain. The muscle aches are often severe, and occur in the thighs, hips, back and sometimes the shoulder. Some patients will develop coughing and shortness of breath within a few days. Others may go for as long as a week with the other symptoms before developing a cough and shortness of breath, followed by the abrupt onset of respiratory distress, often severe and fatal. Mortality is about 40 to 50 percent of people who get HPS disease.