Bat declines in the Northeast, the most severely affected region in the United States, have already exceeded 80 percent. G. destructans has reached Indiana and Ontario, Canada, Lorch said, and could shortly arrive in Wisconsin.

Confirming G. destructans as the cause of white-nose syndrome could not only support research into various disease management strategies for bats, Lorch added, but also aid those trying to predict how fast and far it will spread. The results could further help explain why G. destructans is deadly to bats in North America, but not to bats in Europe.

One likely explanation is that long-term exposure in Europe has caused bats to evolve to coexist with the fungus. Because the fungus was recently introduced to North America, the severity of white-nose syndrome in bats on this continent may reflect exposure of naïve bat populations to a novel pathogen.

“Disease involves the interaction of the pathogen, the host and the environment,” says Lorch, “and understanding their interactions will be essential for mitigating the effects of white-nose syndrome. Identifying G. destructans as causing the disease will help direct future research toward elucidating what makes the fungus pathogenic, what makes North American bats susceptible, and what environmental factors are important for disease progression and transmission to take place.”