YOSEMITE -- A West Virginia resident is the third person to die from a rodent-borne disease after staying at Yosemite National Park, bringing the total number of cases to eight, park officials reported Thursday.
Park officials have raised to 25,000 the number of people who might have been exposed to hantavirus pulmonary syndrome, a lung disease.
The growing number of park visitors known to have contracted the disease last month have been linked to Yosemite's "signature tent cabins" in Curry Village, all 91 of which were closed last week.
Park employees are attempting to contact the nearly 12,000 people who visited those areas this summer and urge them to seek immediate care if they develop symptoms, park spokesman Scott Gediman said.
Park officials have been trying to get in touch with the 10,000 people from around the world who may have been exposed to the potentially deadly virus by staying in the luxury tent cabins since mid-June.
It can take up to six weeks for symptoms to develop. People initially may feel like they are getting the flu, with fatigue, fever, chills and muscle aches. But after a few days, their health may deteriorate rapidly.
One mild case of hantavirus was diagnosed in an individual who stayed in several of the park's High Sierra Camps, including Tuolumne Meadows, according to the California Department of Public Health.
The person who stayed in the High Sierra area "exhibited very mild symptoms," Gediman said. "He never was hospitalized, and he recovered."
That person stayed in tent cabins at Tuolumne Meadows Lodge, Merced Lake Camp, Sunrise High Sierra Camp and Vogelsang Camp, and he did some backpacking, officials said.
In addition to the West Virginia resident, others who died included a 37-year-old Alameda County man and a Pennsylvania resident.
The five who are recovering from the disease were California residents. But because Yosemite has so many international visitors, the park service has put out a worldwide alert for doctors to be on the lookout for cases.
A phone line set up for people to ask questions -- (209) 372-0822 -- has been receiving 200 to 500 calls a day. It is open from 9 a.m. to 5 p.m. daily.
All of the infected individuals are believed to have contracted the disease in June, except for the case linked to the High Sierra Camp, where the individual visited in July.
Before the busy Labor Day weekend, the park closed the double-walled signature tent cabins that have been the focal point of the investigation into how the disease is spreading after finding evidence of mouse activity in the gaps between the walls.
Some people have been canceling reservations to visit the park after hearing about the outbreak, but the Ahwahnee and Yosemite lodges were sold out over the Labor Day weekend, Gediman said.
A major cleanup effort was launched at Curry Village, including dismantling the cabins' hard-sided walls.
During the cleanup, park staff found holes chewed in the foam insulation of the cabins. A further investigation revealed several mouse nests and other evidence of rodents embedded in the walls, said Danielle Buttke, a park service public health official.
Hantavirus is spread by inhaling microscopic particles from the dried urine or feces of an infected rodent, most commonly deer mice.
There have been about 65 known cases of hantavirus in California since it was identified in 1993. Roughly one in three people die from the disease.