In Fresno, Calif., up to 10,000 guests who stayed in certain log cabins may have been exposed to a deadly mouse-born hantavirus at Yosemite National Park.

So far, six people have been infected, and two of them have died. The illness begins with flu-like symptoms that can take up to six weeks to incubate before severe respiratory and organ failure. There is no cure for the virus, and anyone suffering from these symptoms must be hospitalized.

These park cabins hold up to four people. Park spokesman Scott Gediman said Friday that this can estimate that up to 7,000 more visitors might have been exposed. The park is receiving 1,000 phone calls a day from frightened visitors.

The park company Delaware North Co. sent letters and e-mails to roughly 3,000 people whom had reserved these specific cabins between June and August, warning them that they may have been exposed.

More than 36 percent of people who contract this rare illness will die from it. According to the Centers for Disease Control and Prevention (CDC), there had been about 600 cases of Hantavirus in the U.S. from 1993 to 2011, and one third of them were fatal.

Dr. Manny Alvarez was asked, “What makes this virus such a dangerous virus?”

Alvarez replies, “It makes it dangerous because there is no treatment. If you get a severe pulmonary infection, there’s really no treatment for it. You end up with almost a terminal case of a flu, where you really have no oxygen going into your lungs, your heart fails, and then you die.”

What makes this story such a huge deal is that the virus was concentrated where there was a huge exposure to people.

Park officials had disinfected all 400 of the Curry Village cabins when the outbreak was first detected earlier this month. When the outbreak was narrowed to 91 insulated cabins, the California Department of Public Health ordered them to shut down.