Friday, 17 July 2026, 6:59
San Diego County health officials have announced a potential exposure to multidrug-resistant tuberculosis (MDR-TB) at California State University San Marcos and on a Sprinter train. The exposure period spans from December 15, 2025, to May 14, 2026, on the university’s main campus, with additional brief exposures on the Sprinter in late May 2026.
According to the county’s Tuberculosis Prevention and Care Program, the exposure occurred at CSUSM’s main campus at 333 S. Twin Oaks Valley Road in San Marcos. Brief exposures were also reported on the North County Transit District Sprinter, eastbound between Melrose Drive and Civic Center – Vista stations, between 10 a.m. and 3 p.m. on May 18, 20, 26, and 27, 2026. Officials note that TB transmission is more likely during prolonged contact, and short periods on the Sprinter are not considered high-risk, though riders with certain health conditions may face increased danger.
Dr. Sayone Thihalolipavan, county public health officer, emphasized that MDR-TB is treatable with the right medication. “Multi-drug-resistant tuberculosis can be more complicated and lengthier to treat since it does not respond to the usual medicines,” he said. “The good news is that TB, including drug-resistant TB, is treatable and curable with the right medication.”
County health officials are working with California State University San Marcos to notify students and staff who may have been exposed. This information is being shared to help anyone who may have been exposed to discuss the risks with their healthcare provider. Anyone who believes they may have been exposed, or healthcare providers caring for those with known exposures, should call the County Tuberculosis Control Program at (619) 692-8621 for guidance, especially if they test positive for TB following the exposure. Standard TB medications are not effective when treating multidrug resistant TB, and people infected with this type of TB require treatment with alternate medications. TB spreads through the air when a person with TB coughs, speaks, sings or breathes near others. People who have been exposed to someone with TB should get tested. Anyone with symptoms of active TB, including persistent cough, fever, night sweats or unexplained weight loss or those who are immunocompromised should see a medical provider promptly to rule out active TB disease and to discuss treatment. “Multi-drug-resistant tuberculosis can be more complicated and lengthier to treat since it does not respond to the usual medicines,” said Ankita Kadakia, M.D., County Deputy Public Health Officer. “The good news is that TB, including drug resistant TB, is treatable and curable with the right medication. If you believe you may have been exposed, please contact the County Tuberculosis Department right away. Early screening and treatment are important to help protect your health and the health of our community.” Active TB disease can often be prevented through the diagnosis and treatment of a latent TB infection. People who test positive without symptoms should get a chest x-ray to rule out active TB and talk to a medical provider, as they most likely have latent TB infection. Those with latent TB are not yet sick but can prevent future illness by completing a short course of medication. LTBI treatment for people exposed to MDR TB involves different medications than the standard LTBI therapy.
San Diego County has seen a steady rise in active TB cases since 2020, from 193 cases that year to 265 in 2025. MDR-TB remains less common, with three cases in 2024 and two in 2025. An estimated 175,000 county residents have latent TB infections, and without treatment, 5% to 10% may develop active disease. The current case is not linked to any previously announced MDR-TB exposures, including earlier potential exposures at the Iglesia Ni Cristo church in Miramar and at Sunset Elementary School in San Ysidro.
Tuberculosis is an airborne disease spread through inhalation of bacteria from an infected person. It can be difficult to diagnose, and people may be sick for months before detection. MDR-TB does not respond to standard medications, requiring alternative treatment regimens. Congregate settings like schools increase exposure risk.
If you believe you may have been exposed, contact the County TB Prevention and Care Program at 619-692-8621 for early screening and treatment. Early action is crucial to protect individual and community health.
