As many as 10,000 visitors to Yosemite National Park may have been exposed to a deadly disease called Hanta virus say federal health officials. Letters have been sent to about 3,000 individuals who stayed in the ignature Tent Cabins in the Curry Village section of the park warning them that they may have been exposed and to keep alert for Hantavirus symptoms. The U.S. Centers for Disease Control and Prevention (CDC) places the estimate of people who may have been exposed to the virus at 10,000 including not only those who booked stays in the tend cabins but by calculating the number of guests they brought with them as well. The Signature Tent Cabins have been shut down indefinitely following the Hantavirus outbreak which has killed at least two and sickened six. Additional cases are suspected. Hantavirus is transferred to humans when they breate air contaiminated with the virus or come in contact with saliva, urine or droppings from contaminated rodents. In Yosemite the virus is suspected of having been transferred by deer mice. The disease can incubate for up to six weeks until common symptoms occur often confusion with the flu, headaches, muscle aches, stomach problems, dizziness, chills and later more severe problems including coughing and shortness of breath. It is estimated that about 20% of the mice in Yosemite are infested with Hanta.