The California Department of Public Health (CDPH) has provided more details on the six cases of Hantavirus Pulmonary Syndrome (HPS) – or more specifically Sin Nombre virus (SNV) – that originated in Yosemite Valley.

As reported by examiner.com, four of the recent Yosemite National Park visitors, including both fatalities, lodged in the “signature cabins” – operated by Delaware North Companies (DNC) – in the Boystown area of Curry Village between June 10 and Aug. 24, one lodged in an unspecified area of Curry Village and one case is still under investigation.

“CDPH is working closely with the National Park Service and the Centers for Disease Control and Prevention to further investigate the cluster of Hantavirus Pulmonary Syndrome cases in Yosemite and reduce the risk of other visitors becoming ill from this virus,” said CDPH Director, Dr. Ron Chapman. “CDPH is continuing to monitor cases of Hantavirus Pulmonary Syndrome in persons who visited Yosemite National Park.”

Of the six people who visited the park between early June and mid July 2012, five were California residents – from the Sacramento region, San Francisco Bay area and Southern California – and one was a resident of Pennsylvania. While the Pennsylvania patient and one California patient subsequently succumbed to HPS, three have recovered and one remains hospitalized but improving.

Research conducted by the CDC suggests that “the primary method of human infection with hantaviruses is believed to be inhalation of aerosolized virus which is shed in urine, feces, and saliva of infected rodents.”

The CDC also believes that “exposure to infected rodents in closed, confined spaces may be particularly hazardous,” especially while “coinhabiting a room with infected rodents.” This likely explains why on Aug. 28, the CDPH ordered the indefinite closure of all tent cabins in the Boystown area.

The deer mouse, Peromyscus maniculatus, one of the most widespread rodents in the United States and Canada, is the primary reservoir of SNV in much of North America and while human infection with hantaviruses is most often caused by aerosolized inhalation, the CDC states that infection can also occur “when virus or virus-contaminated materials are introduced into broken skin, conjunctivae, or mucous membranes, or perhaps when accidentally ingested with food or water. Infection may also be directly transmitted by bite.”

The first symptoms of HPS usually develop 1-2 weeks after exposure to SNV. Early symptoms resemble the flu and include fever, headache and muscle aches, especially in the thighs, hips, back and shoulders. Two to seven days after the first symptoms begin, HPS patients develop difficulty breathing. Breathing problems can be severe and may require immediate hospitalization. While there is no specific treatment for HPS, early medical attention can increase the chance that an HPS patient will survive.