LOS ANGELES, CA (Catholic Online) - Park officials have sent letters and emails to as many as 1,700 visitors who stayed in the park in June, July and August. They're being warned that they may have been exposed to the disease, and should seek medical treatment if they experience flu-like symptoms.

Hantavirus is spread by contact with rodent feces, urine and saliva, or by inhaling exposed airborne particles.

While it receives four million tourists from all around the world annually, Yosemite park officials are now trying to see if the warning should now include foreign countries.

"We're discussing whether to do that and how to do that," Dr. David Wong, with the National Park Service Office of Public Health says.

Even more worrisome is the fact that the disease can incubate for up to six weeks before flu-like symptoms develop. Hantavirus is fatal in 30 percent of all reported cases, and has no specific treatment. The one good news is that it is not spread from human-to-human, meaning that the disease is not contagious.

The Yosemite cases are atypical, as Hantavirus illnesses are most often isolated events. "We are seeing more than one person who got it in a narrow space and time," he says. "It makes us wonder why, and those are questions we don't have the answers to."

It's estimated that the four victims all bunked in the Curry Village cabins between June 10 and June 20. All four known cases were contracted by people who stayed within 100 feet of each other -- but not necessarily in the same cabins.

Yosemite Park has since sanitized the cabins. Park officials have also gotten the word out to the media that the cause may have been mice in the park.

The Centers for Disease Control had determined over the weekend that a second visitor, a resident of Pennsylvania, died as a result of the exposure to the virus.

Officials also wish to remind visitors that Yosemite Park is a wilderness area - with all the attendant dangers.

"We're very concerned about visitors and employees," park spokesman Scott Gediman says. "But we feel we are taking proactive steps in both cleaning the affected areas and in public education. But it's absolutely impossible to eliminate all risk."

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