A ninth person has been diagnosed with a deadly rodent-borne illness after visiting Yosemite National Park this summer.
Public health officials informed the park Thursday that a California resident has recovered from a hantavirus infection after being exposed to the disease while staying in one of Curry Village's "signature tent cabins" for two nights in early July, said National Park Service spokesman John Quinley.
The victim's name, age, gender and city of residence were not released to the park, according to Quinley.
"The precise reason why this cluster of hantavirus cases occurred at the same time in Curry Village isn't known at this time," Quinley said.
Three visitors who contracted the disease while staying in the same style of cabin during the month of June have died. Another four were hospitalized and are recovering or have recovered.
Among the dead were a 36-year-old Alameda County man, a 45-year-old man from Pennsylvania and a tourist from Kanawha County, West Virginia. Public health officials have said their names are being withheld at the request of their families.
One camper who visited the remote Tuolumne Meadows area of the park in July exhibited mild symptoms of hantavirus and is recovering. That case is not believed to be connected to the Curry Village outbreak.
Hantavirus is spread by contact with the droppings, urine or saliva of infected rodents, primarily deer mice. Sweeping can stir up dried particles into the air and make exposure more likely.
Symptoms of hantavirus pulmonary syndrome begin with fever and aches similar to the flu, but can move on to respiratory problems that can result in death.
The fatality rate for hantavirus is more than 30 percent.
The latest Yosemite victim was diagnosed with a hantavirus infection that did not become hantavirus pulmonary syndrome, or HPS, like the other eight cases, according to the California Department of Public Health.
"Hantavirus infection patients don't show the respiratory symptoms of full-fledged HPS. Hantavirus infection symptoms are similar to those experienced by HPS patients in the first few days of illness," said Dr. Gilberto Chavez, a state epidemiologist and deputy director of CDPH's Center for Infectious Diseases, in an e-mail Thursday.
Meanwhile, Yosemite officials have again increased their efforts to inform visitors who stayed in lodging around the park this summer about the outbreak.
Quinley said more notifications were sent out Wednesday night with the hope they would reach 230,000 more guests who stayed in camps, cabins and hotel rooms in the park this summer.
The park previously attempted to notify 29,000 guests who stayed in Curry Village and Tuolumne Meadows camps from June to September.
The "signature tent cabins" in Curry Village have since been closed indefinitely while inspectors determine how or if they can be permanently sealed from rodents. Park officials said it's suspected the design of the cabins may have contributed to the outbreak.
Other lodging areas and public buildings in Yosemite remained open, but increased rodent trapping and proofing was being conducted in an effort to study the park's deer mice population and prevent any further hantavirus exposures, Quinley said.
"There are mouse traps designed to kill mice, but no sort of mass eradication efforts," he said. "It's more focused on risk prevention and exclusion from buildings and other public areas."
There have been 602 confirmed cases of hantavirus since the disease was first identified in 1993, with 60 of those coming from California.
The only two previous cases of hantavirus connected to the park originated in Tuolumne Meadows, one in 2000 and the other in 2010, both of which did not result in a fatality.
Tuolumne County Public Health Officer Dr. Todd Stolp said Thursday there have been no confirmed cases of hantavirus in the county this summer, but tests have been ordered.
Under state law, health care providers are required to report cases of hantavirus to public health officers within 24 hours of confirmation.