A team of scientists explained that the fungus that causes the white-nose syndrome (WNS) in bats kills the animals by increasing their bodies' consumption of energy, the USGS Newsroom reported.

According to the United States Geological Survey's National Wildlife Health Center, the disease comes from the white fungus known as the Pseudogymnoascus destructans. The disease first appeared in the northeastern part of the U.S. during the winter season between 2007 and 2008 and has caused the deaths of millions of bats.

WNS has been attributed to the 80 percent decline in the population of bats in the U.S. region.

The government agency explained that bats infected with the disease develop white fungal growth on their muzzle and wings. The disease also affects their behaviors during hibernation season.

For years, scientists have been trying to determine how WNS kills bats. Through a joint investigation by the USGS and the University of Wisconsin, scientists were able to take a closer look at how the disease affects the animals.

The researchers conducted the study by creating a model to compare the conditions of healthy bats and those infected with the disease.

They discovered that WNS increases the amount of energy used by the bats when hibernating during winter season. This is particularly dangerous during this period because bats rely on limited energy supply to survive through winter without eating, according to Science Daily.

If too much energy is consumed or wasted, the bats won't be able to live through the cold season.

As for the white fungal growth on the bats' bodies, scientist said these are actually symptoms of the disease that appear during the advance stages of infection.

"Clinical signs are not the start of the disease," lead scientist Michelle Verant said in a statement.

"They likely reflect more advanced disease stages," she added. "This finding is important because much of our attention previously was directed toward what we now know to be the bats in later stages of the disease, when we observe visible fungal infections and behavioral changes."

Verant noted that the findings of the study and the model the researchers created will be vital in helping scientists develop methods to combat the disease.

"The mechanisms details in this model will be critical for properly timed and effective disease mitigation strategies," she explained.

The report by Verant and her team was published by BMC Physiology, a peer-reviewed journal that features scientific studies on physiological processes.