The first victims were discovered in January 2007. Wildlife surveyors conducting a routine census walked into a cave west of Albany, New York. Instead of the healthy bat colony they’d documented two years earlier, the surveyors found thousands of bodies lying cold and still on the cave floor. The dead bats had fuzzy white spots on their wings, their ears, and especially their noses.

Over the following years, scientists watched in horror as the mystery killer, dubbed white-nose syndrome, spread swiftly and silently through eastern North America. It has wiped out more than 6 million bats in 26 states and 5 Canadian provinces (see map). Northeastern U.S. bat populations have declined by an estimated 80 percent.  

Researchers have been scrambling to find ways to slow the spread of the disease ever since. In May, a team of scientists announced the most hopeful news yet: They had successfully treated 75 bats for white-nose syndrome and released the healthy animals into the wild.

Back in 2007, analysis of the white fuzz found on the dead bats in New York revealed that it was a fungus, now known as Pseudogymnoascus destructans. The fungus thrives in cold, dark, damp environments. It’s widespread in European caves, and although it grows on hibernating bats there, it doesn’t seem to do much harm. A person may have unknowingly carried the fungus from Europe to the cave in New York, where bats had never been exposed to the fungus and had no natural defenses against it. The devastating disease took off from there.

The experimental treatment for white-nose syndrome came from an unexpected source: research on how to keep fruit fresh. Several years ago, microbiologist Chris Cornelison was starting out as a graduate student at Georgia State University. Scientists there were studying a bacterium called Rhodococcus rhodochrous, which is found in soils around the world. 

The bacteria release chemicals called volatile organic compounds, substances that evaporate easily at room temperature. One researcher mentioned to Cornelison that these chemicals prevent the growth of mold—a fungus—on fruit. When dishes of the bacteria are placed in a container with bananas, the organic compounds are released into the air in the container, keeping the fruit virtually mold-free. Bananas in a container without bacteria go moldy.

“I’d just learned about white-nose syndrome through the media, and I’d seen all these photos of dead bats in caves,” says Cornelison. “I thought, if this can prevent mold from growing on a banana, maybe it can prevent it from growing on a bat!” 

Cornelison spent the next few years studying the bacteria’s effect on the fungus that causes white-nose syndrome. It consistently prevented the fungus from growing on lab dishes. “I almost couldn’t believe it,” he says. “Fungus grew all over one set of plates, and none grew on the set exposed to the bacteria.” He repeated the experiment five times to be sure it worked.  

Next he needed to find out if it worked on bats. For that, Cornelison teamed up with U.S. Forest Service wildlife biologist Sybill Amelon. First they gathered healthy bats and did experiments to check that the bacteria didn’t harm the animals. The test on the bats was the same as for the bananas: The hibernating bats slept in a container with the bacteria while the bacteria released their fungus-inhibiting chemicals into the air inside. The bats did fine.  

Then the team brought several dozen sick bats into the lab. All of the bats that didn’t receive treatment died. But more than half of those that spent time in a container with the bacteria recovered.

Finally, the scientists tested the treatment on larger numbers of hibernating bats in the real world. They collected infected bats from four caves in Missouri and Kentucky during the winter. They weighed the bats, checked their wings for infection, and took their temperatures. Then they placed the sleeping animals in coolers just outside the cave. Half of the coolers contained plates of bacteria, and half didn’t—this half was their control. After the bats had slept in the coolers for three days, the researchers hung all of the animals back on the cave walls. They used nets to separate the treated and control bats from the others in the cave. In early spring, they brought the treated animals into the lab.

The treatment helped many of the bats survive the winter and recover from white-nose syndrome. The researchers tested the skin of the treated bats to make sure it was free of fungus, and a veterinary team gave them a clean bill of health before volunteers released them back into the wild.

Ecologists still need to confirm that the bacterial treatment is safe for other cave fungi and animals. If so, the bacteria could be brought into caves to treat thousands of hibernating bats at once. 

Bats with more advanced cases of disease weren’t able to recover even with treatment, so this approach won’t stop white-nose syndrome completely. But it could be a promising tool in the battle against the disease, says wildlife biologist Katie Gillies of Bat Conservation International. “Eight years ago we had no idea what this fungus was, and now we’re testing treatments in the wild,” she says. “It’s pretty amazing how far we’ve come.”