Possible Exposure To Drug-Resistant Tuberculosis Reported In San Diego County

SAN MARCOS, CA — San Diego County's Tuberculosis Prevention and Care Program Friday announced a potential exposure to multidrug-resistant tuberculosis for California State University San Marcos students and staff.

The exposure may have occurred between Dec. 15, 2025, and May 14, 2026 at CSUSM's main campus on 333 S. Twin Oaks Valley Road in San Marcos, a statement from the county read.

Additional brief exposures were reported on the North County Transit District Sprinter, eastbound between the Melrose Drive and Civic Center - Vista stations at various times between 10 a.m. and 3 p.m. on May 18, 20, 26, and 27, 2026.

"TB transmission is more likely during prolonged exposures," the county statement read. "Short periods of contact, such as those on the Sprinter, are not considered highly likely to cause infection. Still, riders with certain health conditions may face increased risk. This information is being shared to help anyone who may have been exposed to discuss the risks with their healthcare provider."

According to the county, tuberculosis can be difficult to diagnose, and people may be sick for months before receiving a diagnosis, which can lengthen exposure periods. This situation involves MDR-TB, a type of tuberculosis that does not respond to standard medications.

"Multi-drug-resistant tuberculosis can be more complicated and lengthier to treat since it does not respond to the usual medicines," said Dr. Sayone Thihalolipavan, county 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."

Tuberculosis is an airborne disease spread through the inhalation of bacteria from an infected person. County health officials said individuals in congregate settings such as schools are at higher risk of exposure.

Those who test positive, but do not have symptoms, likely have latent TB and are advised to get a chest X-ray and consult with a medical provider, health officials said.

TB cases in San Diego County have been on the rise since 2020. Health officials reported 193 cases in 2020, 201 in 2021, 208 in 2022, and 242 in 2023. In 2024, a total of 247 people were reported with active TB disease in San Diego County.

Multidrug-resistant tuberculosis is less common, with three cases in 2024 in San Diego County and two in 2025.

County health officials said an estimated 175,000 in the county have latent TB infections and said that without treatment, 5% to 10% of those people are at risk of developing active TB disease.

People who want more information on this potential exposure should call the County TB Prevention and Care Program at 619-692-8621.

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