San Francisco health officials investigate three active tuberculosis cases linked to Archbishop Riordan High School

Three active TB cases identified since November

San Francisco public health officials have identified three active cases of tuberculosis connected to Archbishop Riordan High School since November 2025, triggering a coordinated response that includes required testing, contact tracing, and temporary changes to on-campus routines.

The infected individuals have not been publicly identified, and officials have not said whether the cases involve students, staff, or other members of the school community. The first case was reported in mid-November, and the person was placed in isolation. Subsequent case detections led health officials to broaden their response and update prevention guidance for the campus.

Testing and contact tracing underway; campus precautions expanded

City health authorities and school leaders have implemented schoolwide screening and a contact investigation designed to identify people who may have had prolonged exposure to someone with infectious TB. Officials have also directed additional mitigation steps while testing continues, including symptom monitoring, indoor masking, and adjustments to some indoor activities.

In parallel with broad screening, contact tracing is being used to prioritize evaluation of individuals at higher likelihood of exposure, reflecting standard public health practice for airborne diseases that typically require sustained indoor contact to spread.

• Required TB testing for students and staff as part of a coordinated screening effort
• Contact tracing to identify and evaluate individuals with higher-probability exposure
• On-campus symptom monitoring and interim masking guidance indoors
• Modified indoor activities intended to reduce transmission risk while screening continues

What TB is — and what “active” versus “latent” means

Tuberculosis is caused by bacteria that can spread through the air when a person with infectious TB in the lungs coughs, speaks, or breathes in close proximity to others for a prolonged period. Public health officials emphasize that brief or casual interactions are less likely to result in transmission than extended indoor exposure.

TB can present as active disease or latent infection. People with active TB may have symptoms such as a persistent cough, fever, and weight loss, and can spread the bacteria to others if their disease involves the lungs or throat. People with latent TB infection are not sick and are not contagious, but can later develop active disease if not treated. Both active TB and latent TB infection are treatable with medication.

Public health officials said the response is focused on identifying potential exposures, ensuring timely testing, and reducing the risk of further transmission while the investigation proceeds.

How this fits into San Francisco’s broader TB picture

Tuberculosis remains a continuing public health concern in San Francisco even though it is far less common than many seasonal respiratory infections. City figures previously reported 91 active TB cases in San Francisco in 2024. The investigation at Archbishop Riordan High School is now centered on determining the extent of exposure on campus, identifying any additional infections, and ensuring treatment and follow-up for those who test positive.