With the number of deadly Hantavirus cases possibly linked to guest accommodations at Yosemite National Park climbing, officials have tried to contact roughly 3,000 summer guests to caution them about the disease.

As of Friday, at least six cases of the rodent-borne disease have been documented among park visitors, Yosemite officials said. Two of the six have been fatal, while the other four have either recovered or are recovering, they added. No information on the visitors who were sickened, such as their names, ages, or hometowns, was released.

In a press release park officials said an estimated 3,000 visitors who stayed in the park this summer "have been contacted through email, mail or phone calls" to alert them to the recent Hantavirus outbreak and to advise them to seek immediate medical attention if they exhibit any symptoms of the virus.

"Early medical attention and diagnosis of Hantavirus are critical," said Yosemite Superintenent Don Neubacher in prepared comments. "We urge anyone who may have been exposed to the infection to see their doctor at the first sign of symptoms and to advise them of the potential of hantavirus."

Along with working to reach guests, the park also closed the 91 Signature Tent Cabins, where four of the sickened visitors stayed. The cabins, which were put in use three years ago to partially replace tent cabins lost to rockfalls, are two-walled, and deer mice have been found nesting within the walls.

Phone calls Friday to both park officials and those with DNC Parks & Resorts at Yosemite, which operates the tent cabins, were not immediately returned.

According to a release from the Centers for Disease Control and Prevention, "an estimated 10,000" people have stayed in the Signature Tent Cabins this summer. "People who stayed in the tents between June 10 and August 24 may be at risk of developing HPS in the next six weeks," the CDC said.

The National Park Service Office of Public Health has been working with the Centers for Disease Control and Prevention "to heighten public health awareness and detection and has issued a call for cases to state and local health departments nationwide," the park release said.

Hantavirus is a rare but serious disease that occurs throughout the United States and is caused by a virus that individuals get through contact with the urine, droppings or saliva of infected rodents, the park said. The types of Hantavirus that cause HPS in the United States cannot be transmitted from one person to another. Early medical attention is critical for individuals who contract Hantavirus.

Along with the outreach to past park visitors, Yosemite officials also have set up a non-emergency phone line -- 209-372-0822 -- for questions and concerns related to Hantavirus, and are distributing Hantavirus information to every visitor entering Yosemite. Notices also have been posted throughout the park.

"The park and public health officials are contacting visitors and raising awareness in the medical community to increase the chances that any additional cases that may be incubating will be successfully diagnosed and treated early," said Dr. Danielle Buttke, an epidemiologist with the National Park Service Office of Public Health.

According to the park release, "Most infections are caused by breathing small particles of mouse urine or droppings that have been stirred up into the air. If the virus is contracted, the symptoms appear one to six weeks after exposure with fever, headache, and muscle ache, and progresses rapidly to severe difficulty in breathing and, in some cases, death."