The Centers for Disease Control and Prevention (CDC) is working with the National Park Service and the California Department of Public Health on an investigation of hantavirus pulmonary syndrome (HPS) in people who stayed at Yosemite National Park during June through August 2012.
On Aug. 31, the CDC issued an official health advisory to inform state health departments and healthcare providers to be alert to the possibility of HPS in patients who may have had recent exposure to rodents or a history of travel to Yosemite National Park during this period.
HPS is an acute, zoonotic viral disease that is spread by contact with infected rodents, primarily deer mice. Most persons with HPS are infected by breathing in small viral particles from rodent urine or droppings that have been stirred up into the air. The fatality rate is approximately 36 percent.
Since June 10, 2012, six confirmed cases of HPS have been associated with staying at Yosemite National Park in California. Two of the ill persons died. Additional suspected cases are being investigated from multiple health jurisdictions. Four case-patients with HPS stayed in Signature Tent Cabins in the Boystown area of Curry Village, and the lodging locations of the remaining 2 case-patients are currently under investigation. These cabins have solid walls on the interior of the cabin and are covered with canvas exterior sides and roof. An estimated 10,000 persons stayed in these cabins from June 10 through Aug. 24, 2012. On August 24, 2012, the tents were disinfected and visitors were relocated. People who stayed in the tents between June 10 and Aug. 24 may be at risk of developing HPS in the next six weeks. Providers are reminded to consider the diagnosis of HPS in all persons presenting with clinically compatible illnesses and to ask about potential rodent exposure or if they had recently visited Yosemite National Park.
All guests who made reservations to stay in these cabins from June 10 through Aug. 24, 2012 (approximately 2,900 persons) were emailed or mailed a health advisory urging them to seek immediate medical attention if they or other persons in their party exhibit symptoms of HPS.
The incubation period for HPS is typically two to four weeks after exposure, with a range of a few days up to six weeks. Symptoms of HPS include an initial prodrome of fever, chills, myalgias, cough, headaches, and gastrointestinal symptoms. Laboratory abnormalities in HPS include thrombocytopenia, leukocytosis, hemoconcentration, hypoalbuminemia, and an increase in serum LDH. Chest radiographs may show bilateral interstitial infiltrates. The disease often progresses rapidly to respiratory distress requiring supplemental oxygen and/or intubation, non-cardiogenic pulmonary edema, and shock. There is no specific treatment available, but early recognition and administration of supportive care greatly increase the chance of survival.
Recommendations include laboratory testing of patients with symptoms consistent with HPS is required to confirm the diagnosis. Because it is a reportable disease in the United States, clinicians suspecting HPS should notify and consult with their state health department about confirmatory testing. HPS-specific testing can be done with serum or whole blood, or with tissue samples in fatal cases.
For additional information about HPS symptoms and diagnosis, visit the CDCs Hantavirus webpage at: http://www.cdc.gov/hantavirus/technical/hps/index.html
The clinical case definition for HPS can be found on pages 39-40 in the CDC document, 2012 Nationally Notifiable Diseases and Conditions and Current Case Definitions at: http://wwwn.cdc.gov/nndss/document/2012_Case%20Definitions.pdf