Microscopic image of Mycobacterium tuberculosis bacteria. Photo credit: Centers for Disease Control.

Riders on Metropolitan Transit System trolleys may have been exposed to tuberculosis on the Orange and Blue lines, the county Health and Human Services Agency announced Thursday.

The HHSA and MTS officials are working to notify riders who used the trolley between June 31, 2022 to December 31, 2022 that they were potentially exposed and are at risk for infection.

Those who rode the Orange and Blue lines on the below schedule may have been exposed:

  • Trolley Blue Line from San Ysidro to 12th & Imperial Transit Center Monday through Friday from 6 a.m. to 6:30 a.m.
  • Trolley Orange Line from 12th & Imperial to El Cajon Monday through Friday from 6:30 to 7 a.m.
  • Trolley Orange Line from El Cajon to 12th & Imperial Monday through Friday roughly between 5:45 p.m. and 6:15 p.m.
  • Trolley Blue Line from 12th & Imperial to San Ysidro Transit Center Monday through Friday roughly between 6:15 p.m. and 7:45 p.m.

People with active tuberculosis are often unaware they have the disease and may be contagious for several months before being diagnosed. TB is transmitted from person to person through indoor air during prolonged contact with an infectious person. Most people who are exposed to TB do not become infected.

“Symptoms of active TB include persistent cough, fever, night sweats and unexplained weight loss,” said Dr. Ankita Kadakia, county deputy public health officer.

“Most people who become infected after exposure to tuberculosis do not get sick right away. This is called latent TB infection,” she said. “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 to determine whether someone has been infected.”

According to the county, once the HHSA is made aware, typically through a test result reported by a medical provider, communicable disease investigators conduct extensive interviews with the patient to determine the length of time they were infected and the locations of potential exposure.

Two other MTS riders with TB were reported in August and September 2022. At this time the HHSA does not have any evidence directly linking the rider most recently diagnosed with TB to the other MTS riders.

People who are infected, and people at high risk of becoming ill quickly after an infection, such as those who are immunocompromised, should discuss treatments with a medical provider, as antibiotics can prevent people with TB infection from becoming sick.

More information on the potential exposure can contact the county TB Control Program at 619-692-8621.

The number of people diagnosed with active TB in San Diego County has decreased since the early 1990s and has stabilized in recent years. There were 192 in 2020 and 201 people reported with active disease in 2021. Preliminary data shows 208 people were reported to have active TB disease in 2022. An estimated 175,000 people in San Diego County have latent TB infections and are at risk for developing active TB without preventive treatment, health officials said.

City News Service contributed to this article.