San Diego County health authorities notified the public Friday of a potential exposure to multidrug-resistant tuberculosis (MDR-TB) involving people who attended California State University San Marcos and a small number of North County Transit District Sprinter riders.
The county’s Tuberculosis Prevention and Care Program said the primary exposure window on the CSUSM main campus at 333 S. Twin Oaks Valley Road ran from Dec. 15, 2025, through May 14, 2026. Additional brief exposures were reported on the Sprinter eastbound between the Melrose Drive and Vista Civic Center stations at various times on May 18, 20, 26 and 27, 2026.
What residents should know
County officials emphasized that prolonged contact raises the greatest risk for TB transmission and that short interactions on transit are generally less likely to cause infection. Still, people with certain medical conditions may face higher risk and should consult their health care providers.
"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, San Diego County public health officer. "The good news is that TB, including drug-resistant TB, is treatable and curable with the right medication."
The county noted that TB can be difficult to diagnose and that undiagnosed illness may last months, potentially lengthening the period during which others could be exposed.
Where and when exposures were reported
| Location | Dates | Notes |
|---|---|---|
| California State University San Marcos (333 S. Twin Oaks Valley Rd.) | Dec. 15, 2025–May 14, 2026 | Primary campus exposure window |
| North County Transit District Sprinter (eastbound between Melrose Dr. & Vista Civic Center) | May 18, 20, 26, 27, 2026 | Brief, intermittent exposures during daytime hours |
Advice for students, staff and transit riders
- People who were on the CSUSM main campus during the stated window should consider discussing TB screening with their clinician or contact the County Tuberculosis Department.
- Riders who used the Sprinter between Melrose Drive and Vista Civic Center on the listed dates should assess their risk—those with weakened immune systems or other health conditions may warrant testing.
- Early screening and, if needed, treatment are key to preventing spread; county officials stressed that TB, including drug-resistant forms, can be cured with appropriate therapy.
The county did not provide additional case counts or identify affected individuals in its public statement. Health authorities urged anyone who believes they may have been exposed to reach out to the County Tuberculosis Department immediately.
San Diego residents who are unsure about their risk can contact their health care provider or the county for guidance on testing and next steps. Local colleges and transit agencies were not reported to have released separate statements at the time of the county notice.
