Aug. 30, 2012 -- Health officials have announced two new hantavirus victims, bringing the total number of people who contracted the deadly airborne disease at Yosemite National Park to six. The disease has killed two people since July, prompting park officials this week to close 91 tent cabins. They've also scrambled to send health advisory emails to thousands of campers who visited the cabins this summer.
But given the park's previous brush with the virus, it's not clear whether officials have done enough to prevent the disease and inform guests – or whether they're spreading accurate information.
The disease comes from inhaling or ingesting particles of mouse feces or urine and has a 40 percent mortality rate.
Although it's not clear how long the virus survives outside the mouse's body, Dr. William Schaffner, the chairman of preventive medicine at Vanderbilt University Medical Center, said that when the mouse feces and urine dry, they become more dangerous because they can easily be carried into the air and breathed in.
But Schaffner's information directly conflicts with what Yosemite park ranger Kari Cobb told ABCNews.com on Wednesday: "As soon as it hits sunlight or dries, then it kills the virus," she said. "It's something that has to be contacted relatively quickly after leaving the mouse's body."
She was not available on a subsequent call to her office to discuss where she got her information.
Despite an email sent out this week to warn 3,000 campers who stayed in the mouse-infested cabins, this isn't the first time Yosemite has had a hantavirus case originate on its campgrounds.
A 54-year-old woman was hospitalized in Sept. 2010 after ten days of "abdominal pain, fever, nausea and shortness of breath", according to a 2010 California Department of Public Health annual report. She was diagnosed with hantavirus about two weeks after a visit to Yosemite, and noted that she saw mouse droppings on a table and watched one or two mice run across the floor.
The woman survived, but her illness sparked a hantavirus risk assessment for the park's Tuolumne Meadows campsite, which California Watch posted online. CDPH concluded that the park lacked a protocol for mouse prevention, was using inadequate sterilization methods, and had tents with gaps between the walls and the floor or other openings that could allow mice to get inside.
The document also suggests providing each cabin with hantavirus information, which would warn them to avoid contact with mice and report infestations to park rangers.
But campers including Salomon Varela, who visited the park days before officials announced that a camper exposed to hantavirus at Yosemite died, said no such information was provided.
"I would have liked at least a warning so I could have been vigilant about it," said Varela, who brought his 2-year-old son and allowed him to play in the dirt and under the tent during their trip.
Varela said he read about the disease when he got home, the same day his son came down with a 102-degree fever. He took the toddler to the doctor's office and waited three days for the fever to subside before he could relax.
He likened the situation to beach lifeguards who see a shark in the water but don't tell the swimmers.
"Where's the huge sign?" Valerna said. "They're warning people about the falling rocks, the bear, to stay on the trail. Why not the virus outbreak?"
Cobb said park officials didn't know about the hantavirus cases during the dates Varela visited Curry Village, Aug. 12, 13 and 14. Park officials found out on Aug. 16, the same day they sent out the news release, she said.
Jeena Galvin-Martin, who has visited Yosemite annually since she was a child and stayed in a Signature Cabin with her two young children in early August, said she's never been warned about hantavirus at the park.
"It's nature, I know, but I've never really heard of anything like this before," she said, adding that she's been nervously watching her 3-year-old and her 11-year-old for signs of the illness since she heard about the scare.
The virus takes one to six weeks to incubate, leaving people frightened and uncertain that they could come down with it long after leaving the park. Flulike symptoms -- chills, muscle aches, fevers -- initially appear, and the disease progresses rapidly. Within a day or two it can be very difficult to breathe. People who stayed at the campsite have been urged to visit their doctors at the onset of any symptoms.
This week, officials sent health advisory emails out to the 3,000 people who stayed in the 91 "Signature Cabins" from June 10 through Aug. 24. The Signature Cabins were built in 2009, but have a structural problem that allows mice to get in. The cabins have been vacated and are being cleaned and retrofitted to become "completely mouse-proof," Cobb said.
The park is also receiving 1,000 calls a day to its hantavirus hotline, which was set up Tuesday to field questions from worried campers, according to the Associated Press.
Valerna said he was so angry no one told him about the virus when he was a park guest that he called Yosemite on Tuesday and pretended he wanted to make a trip reservation just to see whether the park officials on the phone would warn him. They didn't, even when he asked whether anything dangerous was going on, he said.
"I said, 'Hey, listen, I just came from there. I know about the virus outbreak,'" Valerna said, prompting the official to tell him about the mice trappings and construction. "Somebody died in July. That's all I need to know."
But Schaffner said there are so many factors at play with hantavirus that it's impossible to prevent completely – even if the tent is reasonably clean.
In fact, hantavirus is not necessarily an outbreak as much as it's a collection of factors that resulted in a few human cases, he said. The number of mice and people in a given area as well as the drought and water availability indoors were all probably factors at play. He added that confined spaces offer more opportunity for an individual to inhale an "infectious dose" of the virus because it's more concentrated indoors than in the open air.
"I don't think there's anyone to blame," he said, adding that if park officials warned everyone and only four known cases occurred, they would be considered alarmist. "They're damned if they do, damned if they don't."