The deaths of millions of bats in the United States and Canada due to 'white nose syndrome' over the last few years has been linked to a fungus that came from Europe, scientists have reported.

In North America, more than 5.7 million bats have died since 2006 when white nose syndrome was first detected in a cave in upstate New York. The disease does not pose a threat to humans but people can carry fungal spores, so while it's not known exactly how the fungus crossed the Atlantic, it was likely brought accidentally introduced by tourists. Spores are known to stick to people's clothes, boots and caving gear.

Why European bats have not died off en masse from white nose syndrome is unknown. It's possible they developed immunity to the fungus or learned to avoid places that favor the spread of the disease. 

Study: Fungus Behind Bat Die-off Came From Europe - OfficialWire News Bureau