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Hantavirus outbreak at Yosemite considered 'unprecedented'

August 29, 2012 |  7:13 am

Health officials described the outbreak of hantavirus at Yosemite National Park as rare as the park took steps to warn the public.

Jana McCabe, a Yosemite park ranger, called the hantavirus outbreak "unprecedented."

"We take this extremely seriously," she said. "We want to know what's going on."

After learning that a Pennsylvania visitor's death was caused by hantavirus, Yosemite officials sent emails Monday evening to those who stayed in the "signature tent cabins" in Curry Village between mid-June and late August, said park spokesman Scott Gediman. Letters were sent to visitors whose email addresses were not on record.

The fatality marked the third confirmed case of the rare rodent-borne disease linked to the park. Last week, park officials said a 37-year-old Bay Area man had died and an Inland Empire woman in her 40s was recovering after being exposed to the virus. Park officials believe there may be a fourth case but had yet to receive confirmation Tuesday.

All four stayed separately at the signature tent cabins in June, Gediman said. Officials have traced the outbreak to deer mouse droppings in the area.

Repeated cases of hantavirus at the same location within a year is "very rare," said Dr. Barbara Knust, an epidemiologist with the Centers for Disease Control and Prevention. There have been 587 cases of human infection from hantavirus recorded between 1993, when the virus was first identified in the Four Corners area, and 2011, according to the CDC. About one-third have been fatal.

Transmitted through urine, droppings or saliva of infected rodents, hantavirus pulmonary syndrome takes between one and six weeks to manifest itself in humans, officials said. The symptoms — fatigue, fever, muscle aches, nausea, vomiting and abdominal pain — are often confused with the flu, Knust said, but can quickly worsen as one's lungs begin to fill with fluid.

In general, Knust said, the virus is transmitted when people come in contact with an enclosed area that has been infested. The disease is not spread from human to human, officials said.

Hantavirus exposures have been traced to Yosemite twice before, in 2000 and 2010, McCabe said. Neither case, linked to lodging in Tuolumne Meadows, was fatal.

After the 2010 case, park officials worked with public health authorities to reevaluate existing hantavirus prevention protocol, McCabe said. The updates, including changes to cleaning policies, were finalized in April.

For instance, McCabe said, although the cabins were always cleaned after guests checked out, visitors used to be able to sweep out their cabins daily, potentially stirring up dust carrying the virus. Park officials trained in how to handle mouse droppings now do that task.

And although officials are still trapping and testing deer mice across the park to determine what caused this outbreak, McCabe said, they are "pretty confident that it's not a cleanliness issue."

"We've reviewed the cases; we've reviewed the cleaning methods," she said. "It makes you start wondering, what has changed? What is going on in the environment? That's really the question."

After confirming the first two infections earlier this month, Yosemite officials began catching deer mice and disinfecting the Curry Village cabins. They also contacted health authorities.

Park officials learned of the second fatality Friday, McCabe said. The Pennsylvania man's doctor didn't initially suspect hantavirus, but after hearing of the Yosemite cases he confirmed that the deceased patient had recently traveled to the park.

The park has since stepped up its response, implementing "rolling closures" of the cabins for deep cleaning, McCabe said. Crews are tearing down interior walls to look inside and repairing holes where mice could get into the structures.


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