Patrons at 24-Hour Fitness gym in Vallejo are on edge after a member tested positive for tuberculosis.
Solano Public Health Officials notified the club on June 16 that a member was infected with the disease.
A club spokesperson refused to answer why it took two weeks to notify other members.
On Friday, county health officials reached out to anyone who was in the club at the same time as the infected patron.
"Everyone checks in so that's how we know who was in the club while he was there," said Dr. Michael Stacey with the Solano County Health Department.
Members said they have never been concerned about potentially contracting anything at the club before.
"I'm not really personally worried," Vallejo-resident Steve Freund said. "You have to be close to get it. But still, this happens."
The Vallejo gym is located on Sonoma Boulevard.