Microscopic view of the bacteria that causes tuberculosis. Courtesy of the National Institute of Allergy and Infectious Diseases (NIAID).

The county’s Tuberculosis Program was working with the Metropolitan Transit System Tuesday to notify riders of the trolley’s Blue Line that they were potentially exposed to and are at risk for tuberculosis.

The exposure happened between Jan. 27 and Feb. 29 of this year, and the specific impacted routes are:

  • The Blue Line between 24th Street Transit Center and Barrio Logan Transit Center, on Monday to Friday, on an inconsistent schedule but typically between 10:30 a.m. and 2:30 p.m. in the above time frame
  • The Blue line between San Ysidro Transit Center and Old Town Transit Center roughly between 5 a.m. and 7 a.m., and from Old Town to San Ysidro between 6 p.m. and 7 p.m. on Friday, Feb. 16

Since exposures occurred at inconsistent hours, the likelihood that any rider had long cumulative exposure times is low, according to the county. These exposures are not known to be associated with any previously reported exposures on the MTS system.

TB is an airborne disease that is transmitted from person-to-person through inhalation of the bacteria from the air. People with frequent and prolonged indoor exposure to a person who is sick with TB should get tested.

“Symptoms of active TB include persistent cough, fever, night sweats and unexplained weight loss,” Dr. Wilma Wooten, county public health officer, said in a statement.

“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 tuberculosis 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 in determining whether someone has been infected.”

Taking medicines for latent TB infection can cure the infection and keep people from ever getting active TB disease.

According to the county, the chance of TB infection is highest for people with many hours of cumulative indoor exposure to a person who is sick with TB. Brief interactions with an ill rider are less likely to lead to TB infection than are prolonged or repeated exposures.

The County TB Control Program recorded 193 TB cases in the county in 2020, 201 people in 2021 and 208 people in 2022. In 2023, the county recorded 243 people with active TB disease.

An estimated 175,000 people in San Diego County have a latent TB infection and are at risk for developing active TB without preventive treatment, health officials said. People who test positive for TB, but who do not have symptoms of active TB, should get a chest X-ray and talk to a medical provider, as they may likely have a latent TB infection.

Anyone who would like more information on this potential exposure should call the county TB Control Program at 619-692-5565.

City News Service contributed to this article.