SAN DIEGO — County officials are warning Metropolitan Transit System (MTS) riders and staff about a potential tuberculosis exposure on some trolley and bus lines this year.

Those at risk of the disease include riders who used certain blue and green trolley lines from Feb. 16 to Aug. 15, the County of San Diego said in a news release Wednesday.

“Trolley Blue Line between Balboa Ave Transit Center and Old Town Transit Center, and on the Green Line between Fashion Valley and Old Town roughly between the hours 6 a.m. to 12 p.m. Monday to Sunday,” the county said.

Anyone who traveled from April 22 to July 15 on Bus Route 901 via Iris Avenue Transit Center to Palm Avenue, as well as 8th Street between the hours 10 a.m. to 11 a.m. and 6 p.m. to 8 p.m., is also at risk.

Tuberculosis, an airborne disease that is transmitted from person-to-person through inhalation of the bacteria from the air, produces symptoms like persistent cough, fever, night sweats and unexplained weight loss, according to the county.

“Most people who become infected after exposure to tuberculosis do not get sick right away. This is called latent TB infection. Some who become infected with TB will become ill in the future, sometimes even years later, if their latent TB infection is not treated. Blood tests and skin tests are effective to determine whether someone has been infected,” said Wilma Wooten, M.D., M.P.H., County public health officer.

While many riders could have been exposed, it’s not likely that a rider was exposed for cumulative extended times, county officials said.

The last report of TB exposure on MTS transit was in February. That impacted riders who used certain blue and orange lines during a six-month period between June 31, 2022 to Dec. 31, 2022.

For more information on the potential exposure, call the County TB Control Program at 619-692-5565.