Health officials said Thursday they were tracking dozens of potential cases of bat exposure at Salt Lake City’s West High School after it closed its doors on late Wednesday so the custodial staff could sweep the building for an infestation of the flying mammals.

Classes resumed as usual on Thursday morning, after inspections by school and health officials. The number of bats appeared to peak on Tuesday, with an estimated 200 bats being rounded up by West High School’s custodial staff. They also found 50 bats on Monday and 60 on Wednesday.

“The school unfortunately sits in a migratory path for these bats, so every year, these bats come through,” said Salt Lake City School District spokesman Jason Olsen. “The numbers have been a bit larger this year, so that’s why there was some concern between us and the health department.”

Some bats were scooped up midflight by custodial staff with butterfly nets, said Tom Szalay, who teaches a photo class at the school. Other bats were found snoozing in classroom corners, according to Olsen.

Once the bats are caught, they’re relocated, Olsen said.

The Salt Lake County Health Department is following 30 potential cases of exposure at the school, epidemiologist Ilene Risk said on Thursday.

They said they will continue to search among students, faculty and staff in the coming days for anyone who has experienced a bite, scratch or any other physical contact with the animals, Risk said.

Rabies is the primary concern with bat exposure, Risk said, and those thought to have come into direct contact with bats will be placed on a regimen of a post-exposure vaccine — regardless of their health insurance status.

Most commonly contracted by humans through the bite of a rabid animal, the rabies virus attacks the central nervous system, causing brain damage, according to the Centers for Disease Control and Prevention. Rabies is almost always fatal after symptoms appear.

Bats infected with rabies may fly during the day or be seen resting on the ground, but often show no signs of the virus. If a person has been bitten, health department officials advised cleaning the wound immediately with soap and water, then contacting authorities quickly. 

Although bats have roosted in West High for decades, this year’s number was unusual, so Olsen thinks they may have come through an open window.

“This is something that the school has dealt with for a long, long time,” Olsen said.

For the past eight or nine years, the bat situation has been more limited, after the school underwent a two-year process of sealing up access points — from air vents to open windows.

One or two bats may have been in the school every year since the schoolwide seal-up, but Olsen hadn’t heard of any reports in “quite some time,” he said.

“To see the bats come back in such large numbers was a bit surprising this week,” Olsen said. “That’s why we decided to shut the school, get everybody out of the school and do a thorough inspection.”

— Tribune reporter Kelly Gifford contributed to this story.