From Ars Technica:
White Nose Syndrome, a fungal infection that kills bats by interfering with their hibernation cycle, was first spotted in a cave in New York in 2006. In just four years, it has spread over 1,200 km through the US and Canada, reaching from Quebec to Missouri, and killing off as many as 90 percent of the bats in infected areas. Those precipitous declines would seem to be unsustainable, and a new study in Science indicates that they are indeed: even in many scenarios where the virulence of the disease tails off, a common species of bat appears headed for regional extinction, perhaps in as little as 15 years.
This has even managed to get a decent amount of mainstream reporting over the last 2 years. The focus has been on the little brown bat, because we’ve got population numbers going back 30 years, so you can chart trends. Other species of bat also appear to be affected, though there isn’t enough historical data to show exactly what’s happening there.
White Nose Syndrome is not really understood, so it’s still not clear what is actually killing off the bats.