San Francisco Ramps Up TB Testing After Outbreak at Private High School

More than 50 latent cases identified in addition to 3 active cases at Archbishop Riordan High School

Jan. 30, 2026 at 7:47pm by Ben Kaplan

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San Francisco health officials have identified more than 50 cases of latent tuberculosis tied to an outbreak at Archbishop Riordan High School, in addition to 3 active cases that have already been reported. The school has canceled in-person classes for a week and will conduct hybrid learning through much of February as a result of the outbreak.

Why it matters

Tuberculosis is a serious infectious disease that can be fatal if not properly treated. The high number of latent cases identified at the school raises concerns about the potential spread of the disease within the school community and the broader San Francisco population if the latent cases progress to active TB.

The details

The first active case connected to Riordan High School was reported in November, but officials said the individual was isolated and the risk to the public was low. However, further investigation has now uncovered more than 50 additional latent TB cases at the school. Latent TB is not contagious, but can develop into active TB if left untreated. Riordan administrators have canceled in-person classes for a week and will conduct hybrid learning through much of February in response to the outbreak.

  • The first active case connected to Riordan High School was reported in November 2025.
  • San Francisco health officials identified more than 50 latent TB cases at the school in January 2026.

The players

Archbishop Riordan High School

A private Catholic high school in San Francisco where a tuberculosis outbreak has been identified.

San Francisco Department of Public Health (DPH)

The local public health agency that is conducting a large-scale TB contact investigation and response related to the outbreak at Riordan High School.

Dr. Dan Kelly

A San Francisco pediatrician who noted that finding so many latent TB cases at a high school would be highly unusual.

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What they’re saying

“Active TB disease is treatable and curable with appropriate antibiotics if it is identified promptly. Some cases will require hospitalization and there is a greater than 10% case fatality rate in San Francisco.”

— San Francisco Department of Public Health (sfchronicle.com)

“Years ago, when high schools used to require TB testing for students, I wouldn't find one latent TB (case) per year. Maybe one every two years.”

— Dr. Dan Kelly, San Francisco Pediatrician (sfchronicle.com)

What’s next

The San Francisco Department of Public Health has instructed all Riordan High School staff and students to get tested for tuberculosis, regardless of symptoms, and to stay home if ill until they receive medical clearance to return.

The takeaway

This TB outbreak at Riordan High School highlights the importance of vigilant disease monitoring and testing, especially in close-knit school communities, to prevent the potential spread of serious infectious diseases like tuberculosis. The high number of latent cases identified underscores the need for proactive public health measures to address this outbreak.