WASHINGTON The National Park Service has dispatched a top Colorado-based epidemic specialist and a Washington-based public health official to investigate the dangerous airborne disease that recently killed two Yosemite National Park visitors and potentially endangers others.
About 1,700 Yosemite visitors who stayed in the park's privately run Curry Village "signature" tent cabins since mid-June are being warned of their potential exposure, park officials said Tuesday. The tent-dwellers are being advised to watch for signs of the often-lethal hantavirus pulmonary syndrome, caused by proximity to infected rodents.
"We're asking people that if they exhibit any signs of the disease to seek immediate medical attention," Yosemite spokesman Scott Gediman said Tuesday.
Though no definitive proof yet connects the Curry Village tents to the recent hantavirus cases, three individuals known to have contracted hantavirus this year had stayed at the popular Yosemite facilities in June. Two died. Officials say they have also identified a probable fourth Yosemite hantavirus patient.
Already, this makes the Yosemite hantavirus episode one of the Park Service's most severe public health challenges.
"Most cases of hantavirus occur as isolated cases; the cluster of cases associated with Curry Village is unusual," Dr. David Wong, a commander in the U.S. Public Health Service and chief of the epidemiology branch of the Park Service's Office of Public Health, said Tuesday.
In all of 2011, the Park Service recorded 50 public health "incidents" nationwide. These ranged from E. coli infections at the Grand Canyon and measles at Bryce Canyon to valley fever, a fungus that enters the lungs. An archaeology student digging in the dust at Pinnacles National Monument in California came down with it.
Though a Yosemite visitor survived a hantavirus bout in 2010, no hantavirus exposures occurred in any National Park Service property last year, according to the Office of Public Health's annual report.
Nationwide, 24 hantavirus cases were reported in 2011 to the federal Centers for Disease Control and Prevention. Half of the patients died, though the average mortality rate since the disease was first identified in 1993 has been about 38 percent. The disease is typically caused by inhaling small particles of mouse urine or droppings that have been stirred up into the air.
The illness starts between one and six weeks after exposure, marked by fever, chills and muscle aches. Fluid eventually fills the lungs, with one survivor telling the CDC that the feeling was like "a tight band around my chest and a pillow over my face."
To oversee the new Yosemite investigation, veterinary epidemiologist Dr. Danielle Buttke arrived on Sunday from Fort Collins, Colo., and public health specialist Adam Kramer, a lieutenant commander in the U.S. Public Health Service, arrived from Park Service headquarters. California Department of Public Health staffers have also been on scene.
"Staff from various offices at Yosemite are putting a great deal of time on this issue as well," U.S. Public Health Service Capt. Charles Higgins, director of the Park Service's Office of Public Health, said Tuesday.
Among other tasks, Buttke and her team have been trapping and testing the deer mice prevalent in Yosemite Valley. Between 15 percent and 20 percent of the deer mice population test positive for hantavirus, Gediman said, though he noted that the likelihood of human exposure also depends on factors like the rodent's population density and the animal's ability to get into tent cabins. Additional rodent-proofing and trapping measures have been instituted since the hantavirus patients were identified.
The concession company Delaware North, which operates the Curry Village tents, sent emails to most of the Curry Village signature tent visitors by Monday night, and plans to send follow-up letters by today to those without email contact information. Park rangers are also handing out brochures to visitors.