Bats carry many of the world’s most virulent human viruses: rabies, Ebola, Marburg, Nipah, and Hendra. In the wake of COVID-19 (and its bat-borne virus, SARS-CoV-2), scientists are searching for why these viruses manifest so dangerously in humans.
Cara Brook holds a bat while doing field research
Cara Brook holds bat teeth samples
Integrative biology professor Cara Brook ascribes the virulence to bats’ unique status as flying mammals. Bats have uniquely fine-tuned immune systems to cope with the intense stress they incur during flight.
“Flight is really pushing the physiological boundaries,” said Brook. “A bat in flight will elevate its metabolic rate up to 15-fold from resting. A human running at full speed will double their metabolic rate. It's thought that for flight to have even been evolutionarily possible, bats had to evolve these unique damage control pathways that, as a byproduct, appear to also promote their resilience to aging processes and their tolerance of viral infection.”
Brook is a disease ecologist who studies how pathogens interact with their hosts and the environment. Her 2025 hire represents UC Berkeley’s expanding expertise in zoonoses — infectious diseases that humans contract from animals. This is actually Brook’s second stint on campus; she previously worked with integrative biology professor Mike Boots as a postdoctoral researcher.
“We're lucky to have her here,” said Boots. “She's a very special researcher who goes from the field to pure theory through everything in between. Almost nobody does that, but if you want to understand these big questions about spread and evolution, you need people who are intrinsically multidisciplinary. She's someone who does everything.”
Brook runs a long-term study that tracks viruses in Madagascar’s wild fruit bats. Her goal is to understand what mechanisms underpin transmission, how viruses are maintained in their wild hosts, and what predisposes these viruses to infect humans. Through this effort, she also discovers novel viruses — putting her on the frontline against emerging health threats.
Bats get a bad rap, and local attempts to exterminate them often backfire as the malnourished and understandably stressed offspring transmit viruses at a higher rate. Brook is searching for a new way to deal with zoonotic threats by preparing to test a henipavirus vaccine in an isolated population of wild bats. The test should offer lessons for conservation efforts as well as human health measures. In the wake of the COVID pandemic, many jurisdictions restricted critical strategies like vaccines, mask mandates, and quarantine orders. Brook hopes that preventing zoonotic spillover to humans in the first place will make public health less dependent on finicky political will.
“It's a challenging field to work in,” said Brook. “One is never recognized or rewarded for the absence of something happening. There's no way to be certain that you prevented a future pandemic.”