Mammoth Cave National Park officials say bats infected with a deadly disease have been found in sections of the cave open to public tours.

The disease, first discovered in upstate New York in 2006, has steadily been moving through the country's caves. Since it was first detected, the disease has been blamed for killing more than 5.7 million cave-hibernating bats in eastern North America, according to the U.S. Fish and Wildlife Service. Mortality rates of bats have reached almost 100 percent in multi-year infected caves, according to the agency.

While white-nose syndrome previously had been detected in a section of Mammoth Cave off-limits to public tours, Long Cave, now officials say it has turned up in bats found in the Historic Tour section of the cave.

“We have observed some increase in bat activity, which may be due to the illness,” said park Superintendent Sarah Craighead. “We have also found several dead bats in the last few weeks.”

“It is important to remember that White-Nose Syndrome affects bats, not humans,” added Superintendent Craighead. “As with all our wildlife, we caution visitors not to approach animals, including bats. If contact should occur, please notify a ranger.”

There are more than 400 caves in the national park, and the staff has been testing for the fungal disease since 2009. Access to all caves, including the iconic 390-mile-long Mammoth Cave, is controlled by the Park Service and limited to guided tours and research projects.

Each winter about 25,000 bats hibernate in the park, and officials know that at least 26 of the 400 or so caves are used for roosting. Fourteen of the caves are only used as summer roosts, six are used for winter roosts, and six are used both for summer and winter roosts, park officials say.

Concerned that the disease could sweep through the park's caves, officials in the fall of 2010 established protocols for visitors to follow with hopes they would prevent human transmission of the fungus that causes the disease.

While it's not considered a health threat to humans, white-nose syndrome is deadly to bats, and there are fears that entire species could be eradicated by it. As the disease spreads, its impacts could ripple through ecosystems. Not only are bats efficient predators when it comes to insect control -- some bats can eat up to 2,000 mosquito-sized insects in a single night -- but they in turn are prey for hawks, owls, and skunks, just to name some predators.

Tours and research are continuing at Mammoth Cave National Park, accompanied by extensive education and outreach on WNS, and adherence to approved cleaning methods recommended by U.S. Fish and Wildlife Service.