Pseudogymnoascus destructans is a psychrophilic fungus that causes white-nose syndrome (WNS), an emerging disease in North America. This fungus has caused unprecedented population declines. It has been described also in Europe and Asia, where has not caused significant mortality. The first evidence of WNS in North America is from a photograph of a hibernating bat taken during the winter of 2005-2006 in a cave near Albany, New York. P. destructans develops when body temperature decreases during winter hibernation. This fungus thrives in humid and cold conditions characteristic of caves. Infected bats can develop visible white fungal growth on the nose, ear, and wings, and awaken more frequently from torpor. It leads to physiologic changes that result in weight loss, dehydration, electrolyte imbalances, and the death of bats. The fungi can persist in the environments of underground bat hibernation sites and are believed to spread primarily by the natural movements of infected bats. Also, there is a strong possibility that it may also be transmitted by humans inadvertently carrying the fungus from cave to cave on their clothing and gear. WNS has a big impact on bat populations with high levels of mortality, particularly endangered species. Some populations will take many years to recover. The decline of bats also has an impact on the spread of diseases, since many species of bat feed on insects carriers of several pathogens.