The ailment—named for the white circles of fungus found around the noses of affected bats—was first noticed last January in four caves west of Albany, New York.
It has now spread to eight bat-hibernation sites in the state and to another site in Vermont.
Alan Hicks, a bat specialist with New York's Department of Environmental Conservation (DEC), called the quick-spreading disorder the "gravest threat" to bats he had ever seen.
(Related news: "U.S. Bee Collapse May Be Due to Alien Virus" [September 6, 2007].)
Up to 11,000 bats were found dead last winter, and many more this year are showing signs of illness, Hicks said.
One hard-hit cave went from more than 15,000 bats two years ago to 1,500 now.
"We do not know what the cause is, and we do not know how it was spread, either from cave to cave, or bat to bat," Hicks said. "You have this potential for this huge spread."
Control the Spread
The white fungus ring around bats' noses is a symptom of the disease, but not necessarily the cause.
For some unknown reason, bats that display white nose syndrome deplete their fat reserves and die months before they would normally emerge from hibernation.
New York and Vermont environmental officials are asking people not to enter caves or mines known to house bats until researchers figure out how the infection is spread.
There is no evidence that the disease is a threat to humans, but officials want to take every precaution to avoid it spreading from cave to cave.
Bats are considered particularly vulnerable when they hibernate, a time when they hang together tightly by the thousands.
Indiana bats, an endangered species in the U.S., are especially at risk from the illness.
"Half the estimated 52,000 Indiana bats that hibernate in New York are located in just one former mine—a mine that is now infected with white nose syndrome," the New York DEC wrote in a press release.
But the highest death count so far has been among little brown bats.
"I'm very concerned," Hicks said. "I can only hope that what we're seeing today will dissipate in the future."
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