San Diego County health officials are warning that students and staff at California State University San Marcos may have been exposed to a confirmed case of multidrug-resistant tuberculosis on the university’s main campus between Dec. 15, 2025 and May 14, 2026. Investigators also identified brief passenger exposures on the North County Transit District Sprinter eastbound between the Melrose Drive and Vista Civic Center stations on May 18, 20, 26 and 27, 2026. Officials note that TB spreads through the air, and they stress that short transit encounters are less likely to cause infection, although people with certain medical conditions may face higher risk.
County notifies CSUSM community
According to NBC 7 San Diego, the San Diego County Tuberculosis Prevention and Care Program said the possible exposure occurred on CSUSM’s main campus at 333 S. Twin Oaks Valley Road and confirmed the Sprinter dates. The county described the illness as multidrug-resistant, and County Public Health Officer Dr. Sayone Thihalolipavan cautioned that “multi-drug-resistant tuberculosis can be more complicated and lengthier to treat since it does not respond to the usual medicines.” The county is urging anyone who believes they may have been exposed to seek TB screening without delay.
How contacts are tested and when
Public-health contact investigations typically start with a TB test, either a tuberculin skin test or an IGRA blood test, along with a symptom review. If symptoms suggest possible disease or the test comes back positive, a chest X-ray is usually the next step to check for active TB. The Centers for Disease Control and Prevention recommends that people who have been around someone with infectious TB be tested again about 8 to 10 weeks after their most recent exposure, since an infection may not show up on an initial test. These investigations also help staff identify close contacts who need follow-up, in line with CDC guidance.
Local trends and the MDR context
San Diego County has seen TB diagnoses slowly climb in recent years: 193 cases in 2020, 201 in 2021, 208 in 2022, 241 in 2023 and 247 in 2024, with 265 cases reported in 2025, according to the county’s Tuberculosis in San Diego County: By the Numbers report. Multidrug-resistant TB remains uncommon locally, but county data note a small number of MDR cases in recent years and one extensively drug-resistant case in the past, both situations that call for longer, more complex treatment and close public-health oversight. County estimates also indicate that roughly 175,000 San Diegans live with latent TB infection, which can progress to active disease if it is not treated.
Where to get tested and who to call
Anyone who spent time on the CSUSM campus during the identified window or rode the Sprinter on the listed dates is urged to contact a healthcare provider and consider reaching out to the County Tuberculosis Prevention and Care Program for guidance and testing options. As reported by NBC 7 San Diego, the county has posted a hotline at 619-692-8621 for more information, and its TB webpages outline testing resources and recommended next steps. Officials note that people who test positive but have no symptoms most likely have latent TB and are advised to obtain a chest X-ray and talk with a medical provider about preventive treatment choices.
