White-nose syndrome (WNS) was first documented in New York during the 2006-2007 winter. WNS refers to a white fungus which can be found on the muzzle and wing membranes of affected bats. It has been associated with the deaths of over a million bats in the northeast and eastern U.S. Since the 2006-2007 winter, it has spread to nine states including most recently Pennsylvania and West Virginia. Transmission of WNS is unclear at this time. It is also not yet known if the fungus is the cause of the mortality occurring in these hibernating bats or if it is a symptom. Affected bats do not always have the white fungus but do leave their hibernacula during the winter and typically die.