"We know these bats are rabid," said Dr. Hildy Meyers with the Orange County Health Care Agency. "We want to identify anyone that might have had contact so we can evaluate them."
Officials said most cases of rabies in humans are due to bites from rabid bats, which transmit the virus through saliva.
Symptoms can start out as fever and body aches, as the virus spreads to the central nervous system.
"Unfortunately, once you have the symptoms almost everyone dies of the disease," Meyers said.
However, officials said there is an effective vaccine that is injected into the patient's arm.
So far this year, 11 bats have tested positive for rabies in Orange County, authorities said, which is already one case higher than all of last year combined.
Authorities don't know why the number is so high this year, but are warning people to avoid contact with bats, especially if they're seen in the day or on the ground.
"That's abnormal behavior for a bat," Meyers said. "The chances that it's ill are high."
Anyone bitten by a bat should immediately wash any wound and get medical attention.