Since 2006, when White Nose Syndrome was discovered in a New York cave, the disease has quickly spread through colony-hibernating bat species in eastern North America—and even some populations in the west. This deadly fungus has already killed at least 5.7 million bats in 31 states and five Canadian provinces.

While researchers have sought a solution to the fungus, they haven’t found a magic bullet, yet. But a new study raises hope that there could be a relatively simple solution. As Elaina Zachos at National Geographic reports, new research suggests that the White Nose Syndrome fungus is vulnerable to short bursts of ultraviolet light.

The fungus, Pseudogymnoascus destructans (PD), has evolved to thrive in cool temperatures (between 39 and 68 degrees Fahrenheit) and dark environments—like in bat caves, according to a press release. It doesn't kill the creatures directly. Instead, it grows on the wings, ears and snouts of hibernating bats, irritating the creatures and causing them to wake during the winter.

Bats have just enough fat stored in their tiny bodies to make it through the cold months by hibernating. But each time they rouse, they waste energy and burn too much fat, which leaves them too exhausted to survive through spring.

The disease came from Eurasia, where bat species have evolved to cope with the fungus over millions of years. But North American species don't have the same defenses. After the fungus made the jump overseas, the creatures began succumbing to the fungus at a rapid rate—up to 90 percent in some areas.

As Darryl Fears at The Washington Post reports, researchers found the new treatment after spending years poring over the genome of the fungus. The scientists noticed there was a gap in P. destructans DNA. Unlike six other closely related fungus species, they realized that PD did not have the genes for an enzyme that can repair cells after exposure to ultraviolet light. According to the press release, they found that a low dose of UV-C killed 85 percent of the fungus. A moderate dose of UV, lasting only a few seconds, killed 99 percent of the fungus. The research appears in the journal Nature Communications.

“[PD is] something that has evolved for millions of years in the dark. Its ability to repair damage caused by UV light . . . seems to be entirely lacking in this fungus,” U.S. Forest Service plant pathologist and co-author of the study Daniel Lindner tells Zachos. “I’d go as far as to say it’s a vampire fungus. It doesn’t go up in a puff of smoke, [but] it’s gone down an evolutionary path so far that it’s really a creature of the dark.”

Finding the Achille’s heel of PD is encouraging, but killing the fungus in a Petri dish is only the first step. Treating millions of affected bats in challenging-to-access caves and mines across the continent is much harder. As Fears reports, Lindner is currently working on ways to treat affected bats with UV. “We now have a grant to apply UV light to bats that have white nose syndrome. That’s where we’ll find out if you apply it to bats, does it help,” he says, calling the procedure a “mini-tanning bed” for bats. “All it takes is a quick dose of a couple of seconds.”

Trying to treat a cave of bats individually, however, is time-consuming, expensive and would likely disturb entire colonies. Marm Kilpatrick of the University of California tells Zachos that just flashing an entire bat colony with UV probably wouldn’t do the trick either. While the fungus is often visible on the bats’ snouts, it is also present in the armpits of their closed wings and would not be affected by the UV.

Another option is to set up UV lights that pulse at cave entrances and can flash the bats as they come and go before hibernation, Fears reports. While it would probably only save a small percentage of bats, it might be enough to preserve the colony until a new solution can be found or until the bats develop resistance to the fungus. While some species have declined by 99 percent in affected states, some percentage of bat populations seem to be resistant to the fungus and continue to reproduce in its presence.

Even so, the expansion of the disease range is cause for great concern. In 2016 scientists found that the disease had made the leap to west of the Rocky Mountains. In 2015 white nose was also found in Oklahoma and Nebraska. And last year, it was found in six counties in Texas, the state with the largest bat diversity in the United States. It's feared that an infection there could serve as a passage of the fungus down south to Mexican species and even perhaps to Central and South America.

“We’ve got 15 western species that have the potential to be infected,” Katie Gillies, director of the Imperiled Species Program at Bat Conservation International tells Fears. “Containment is not going to be possible.”

Hopefully, researchers figure out how to shine a little light on the situation, and soon.