Yosemite hantavirus outbreak "unprecedented,"officials say
Yosemite officials are scrambling to understand what caused the hantavirus that has killed two people and sickened at least one other in an outbreak of the rare rodent-borne disease described as "unprecedented."
After announcing Monday that a third case of the disease had been confirmed — resulting in the death of a Pennsylvania man — and a fourth probable, Yosemite officials emailed about 1,700 people who stayed in the park's popular Curry Village, asking them to seek immediate medical attention if they showed the flu-like symptoms of the disease.
Last week, park officials revealed that a 37-year-old Bay Area man died and an Inland Empire woman in her 40s had been sickened after contracting hantavirus in the park. All four people believed to be affected by the disease stayed in Curry Village's "signature tent cabins" in mid-June.
Dr. Barbara Knust, an epidemiologist with the Centers for Disease Control and Prevention, said it was “very rare” to have more than one reported case of hantavirus in the same location in a given year.
“It’s unusual," Knust said, "and so we hope that there won’t be any additional cases reported.”
There were 587 cases of hantavirus recorded nationwide between 1993 — when the virus was first identified in the Four Corners region — and 2011, according to the CDC. Only about one-third have been fatal.
Transmitted through the urine, droppings or saliva of infected rodents, hantavirus pulmonary syndrome takes between one and six weeks to present 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, causing respiratory problems that can be fatal.
Jana McCabe, a Yosemite park ranger, called the outbreak "unprecedented."
"We take this extremely seriously," she said. "We want to know what's going on."
Two other hantavirus exposures have been reported in the park's history, in 2000 and 2010, both in the Tuolumne Meadows, McCabe said. Neither of those cases was fatal.
After the 2010 case, park officials worked with public health authorities and reevaluated their existing protocol to prevent hantavirus, McCabe said. The updates were finalized in April and included changes to cleaning policies like allowing guests to sweep out their own cabins daily. Trained park officials now do that task, McCabe said.
And although officials are still trapping and testing mice 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."
Public health authorities have not advised the park to close Curry Village, McCabe said. Instead, crews are implementing "rolling closures" of the cabins for deep cleaning — sometimes going into interior walls to look for dirt and dust that could carry the disease — and repairing any holes where mice could get into the structures.
Until officials know what caused the outbreak, McCabe said, they're doing all they can to warn park visitors about the disease. Fliers have been posted at all park entrances and campgrounds.
"The No. 1 importance to us is that visitors are safe and feel safe coming here. We want to know what's going on. We want to understand, have things changed?" she said. "All that takes time — to gather the information, to analyze it. That's just a luxury you can't afford."
— Kate Mather