Tuberculosis Outbreak at San Francisco’s Archbishop Riordan High School: What You Need to Grasp

San Francisco health officials are responding to a tuberculosis (TB) outbreak at Archbishop Riordan High School, a private Catholic school near City College. Although the risk to the general public remains low, the situation has prompted extensive testing and a temporary shift to hybrid learning. Here’s a breakdown of what’s happening, what it means, and what steps are being taken.

What’s Happening at Archbishop Riordan?

As of February 20, 2026, three confirmed cases of active TB have been identified within the school community, with the first diagnosed in November 2025 and two more in January 2026. Three suspected active TB cases are under investigation. The San Francisco Department of Public Health (SFDPH) is working closely with the school to manage the outbreak.

Extensive testing has revealed a significant number of latent TB infections. A total of 1,261 tests were conducted among students and staff, with 219 (17%) testing positive for TB. Of those, 204 cases have been confirmed as latent TB, and further testing is underway to rule out active disease in the remaining individuals. Mission Local reports this represents approximately 16% of those tested.

What’s the Difference Between Latent and Active TB?

It’s crucial to understand the distinction between latent and active tuberculosis. Latent TB means a person has been infected with the bacteria, but the immune system is keeping it under control. People with latent TB don’t feel sick and cannot spread the infection to others. However, if left untreated, latent TB can develop into active TB disease, which is contagious.

Active TB typically affects the lungs and can cause symptoms like a persistent cough, fever, night sweats, and weight loss. It spreads through the air when a person with active TB coughs, speaks, or sings.

What Steps Have Been Taken?

Archbishop Riordan High School implemented a TB clearance process guided by the SFDPH. This process has allowed the school to clear 99% of current students and 100% of faculty and on-campus staff from active TB disease, enabling a return to fully in-person learning. The San Francisco Examiner reports the school resumed in-person classes on Monday, February 23, 2026.

All confirmed and suspected active cases are currently receiving treatment, and health officials state there are no contagious cases on campus. The SFDPH has also issued a health advisory to clinicians and held information sessions for pediatricians and community town halls.

Is the Public at Risk?

Health officials emphasize that the risk to the general public remains low. Dr. Susan Philip, San Francisco’s Health Officer, stated that contact tracing and testing are critical to preventing future active cases and protecting long-term health. To date, no related active TB cases have been reported at other San Francisco schools.

What Do Experts Say?

Dr. George Rutherford, a pediatrician and infectious disease specialist at UCSF, described the public health response as “thorough and appropriate.” He noted that the proportion of latent infections is significant, being higher than the typical background rate of around 6% in California and 10% globally.

Rutherford cautioned that the elevated rate could indicate a clustering of cases within the school, potentially linked to specific activities like choir practice where airborne transmission is more likely.

Key Takeaways

• An outbreak of tuberculosis has been identified at Archbishop Riordan High School in San Francisco.
• Three confirmed cases of active TB and three suspected cases are under investigation.
• 204 cases of latent TB have been identified through testing.
• The risk to the general public remains low.
• The school has resumed in-person classes after implementing a TB clearance protocol.