Preserving and restoring natural habitats could prevent pathogens that originate in wildlife from spilling over into domesticated animals and humans, according to two new companion studies.

The research, based in Australia, found that when bats experience loss of winter habitat and food shortages in their natural settings, their populations splinter, and they excrete more virus. When populations break up, bats move near humans to agricultural and urban areas.

“Pathogen Spillover Driven by Rapid Changes in Bat Ecology,” published Nov. 16 in Nature, combines multiple datasets over 25 years. The data includes information on bat behavior, distributions, reproduction and food availability, along with records of climate, habitat loss and environmental conditions. The study predicts when Hendra virus – an often-fatal illness in humans – spills over from fruit bats to horses and then people.

The researchers found that in years when food was abundant in their natural habitats during winter months, bats emptied out of agricultural areas to feed in native forests, and away from human communities.

A second paper, “Ecological Conditions Predict the Intensity of Hendra Virus Excretion over Space and Time from Bat Reservoir Hosts,” published Oct. 30 in Ecology Letters, used data from the Nature study to reveal ecological conditions when bats excrete more or less virus.

While previous research has shown correlations between habitat loss and occurrence of pathogen spillover, these studies together reveal for the first time a mechanism for such events and provide a method to predict and prevent them.

SARS-CoV-2, SARS-CoV-1, Nipah, Hendra and possibly Ebola are all examples of viruses that fatally spill from bats to humans, sometimes after transmission through an intermediate host. In humans, Hendra virus has a 57% fatality rate, and Nipah virus can be up to 100% fatal – though transmission in humans is inefficient.

“Right now, the world is focused on how we can stop the next pandemic,” said Dr. Raina Plowright, professor in the Department of Public and Ecosystem Health at the Cornell University College of Veterinary Medicine, and senior author of both studies. “Unfortunately, preserving or restoring nature is rarely part of the discussion. We’re hoping that this paper will bring prevention and nature-based solutions to the forefront of the conversation.”

Plowright and colleagues are investigating whether the basic mechanisms found in this study apply to other examples of pathogen spillover from wildlife to humans.