This is a story about a virus that infects a fungus.

The fungus causes white-nose syndrome — a disease that’s affecting bats in 29 states, including Kentucky. Bats with white-nose syndrome act strangely; they often lose the fat reserves that are necessary to survive the hibernating winter months, then leave caves in the winter and die.

Scientists estimate that so far, white-nose syndrome is fatal for anywhere from 90 to 100 percent of bats with the disease. Since 2006, it’s killed more than six million bats in North America.

This is a problem with huge implications for the ecosystem. Bats play a major role in insect control. They eat mosquitoes, and could play a role in stopping or slowing the spread of mosquito-borne illnesses, like the Zika virus.

But one of the many barriers scientists are facing in addressing white-nose syndrome is they still don’t know how it spreads. And that’s where the virus comes in.

“We don’t really know where this virus came from,” Marilyn Roossinck said.

She’s a professor of virus ecology at Penn State University, and an author of a new study on the virus. The virus in question (its technical name is Pseudogymnoascus destructans partitivirus-pa) infects the fungus (Pseudogymnoascus destructans) that causes white-nose syndrome. Roossinck said so far, it’s been found on every North American bat with the disease.

But while the fungus seems to be identical on every bat with white-nose syndrome, the virus varies between regions.

“So you can’t really tell where [white-nose syndrome] is moving around because [the fungi] all look exactly the same,” Roossinck said. “The virus has variation in it. So that’s the tool that we’re using now to try to understand how the fungus spreads.”

So, when a bat travels 100 miles from a colony in Kentucky to a colony in Ohio, scientists could be able to trace the particular Kentucky-virus it brought with it and study its trajectory.

Do bats of one species spread white-nose syndrome more readily to others of the same species? Roossinck said the virus may provide those answers, and may even help scientists make inroads into figuring out how to eradicate white-nose syndrome.