California public health agencies are placing renewed attention on tuberculosis (TB) prevention in educational settings following several school-associated exposures and outbreaks. The developments underscore the continued value of risk assessment, targeted testing, rapid public health response and treatment of latent TB infection.

Key California TB Indicators

California TB disease, 2025	Archbishop Riordan HS investigation*	State incidence, 2025
2,150 reported cases	254 positive TB tests; 8 active TB cases; 246 LTBI	5.4 cases per 100,000 residents

*San Francisco Department of Public Health data as of June 4, 2026. Figures may continue to evolve as investigations and follow-up are completed.

School-Based TB Investigations Bring Prevention Back Into Focus

One of California’s most closely watched school-based TB investigations occurred at Archbishop Riordan High School in San Francisco. According to the San Francisco Department of Public Health (SFDPH), 1,407 members of the previously exposed school population had at least one TB test reviewed and validated as of June 4, 2026. Of those evaluated, 254 had a positive TB test, including 8 confirmed active TB cases and 246 people with latent TB infection (LTBI).

The investigation prompted extensive contact tracing, testing, treatment follow-up, and operational changes at the school. The response illustrates the scale of coordination required when TB is identified in a setting where students and staff spend prolonged time indoors.

Other school-associated exposures have also been reported in California. In Fresno County, public health officials identified one active TB case associated with Justin Garza High School and reported that 22 of 169 exposed individuals tested positive for TB infection. In San Diego County, health officials notified families and staff of a potential TB exposure at Sunset Elementary School and offered screening to those considered at increased risk.

California’s Broader TB Context

California reported 2,150 cases of TB disease in 2025, the highest annual count reported since 2013. The statewide incidence was 5.4 cases per 100,000 residents, compared with a national incidence of 3.0 per 100,000. CDPH also reported that most California TB disease in 2025 was attributable to progression from latent TB infection rather than recent transmission.

These data reinforce an important public health principle: identifying and treating latent infection can reduce the likelihood that infection progresses to active TB disease.

How California’s School Screening Framework Works

California uses a risk-based approach for many school employees, contractors, and volunteers rather than requiring universal diagnostic testing. Under California school TB requirements, individuals who fall within covered categories complete a TB risk assessment, and diagnostic testing is performed when risk factors are identified.

1. Risk assessment

A standardized TB risk assessment is completed to identify exposure history and other relevant risk factors.

2. Clinical review

A qualified health care provider reviews the assessment and determines whether additional evaluation is needed.

3. Targeted testing

When indicated, testing may include an interferon-gamma release assay (IGRA) blood test or a tuberculin skin test (TST).

4. Ongoing compliance

For many covered school employees, the risk assessment is repeated at least every four years; testing is based on the assessment result.

For students, California and local jurisdictions use pediatric risk-assessment frameworks and targeted testing. Local health authorities may issue additional requirements or outbreak-specific instructions depending on local epidemiology and exposure circumstances.

Active TB Disease and Latent TB Infection: Why the Distinction Matters

Clinical status	Symptoms	Contagious?	School / public health significance
Active TB disease	May include persistent cough, fever, night sweats, weight loss, or coughing blood	Potentially yes, especially with infectious pulmonary TB	Requires prompt medical evaluation, public health reporting, treatment, and exposure management.
Latent TB infection (LTBI)	Typically none	No	Not contagious, but treatment can reduce the risk of future progression to active TB disease.

What Schools, Families, and Communities Can Take From These Events

• Risk-based screening remains an important prevention tool, particularly for people with known TB exposure or other recognized risk factors.
• People with latent TB infection are not contagious, but identifying and treating LTBI can help prevent future active disease.
• When an exposure occurs, contact tracing and targeted testing help public health agencies focus resources on those most likely to have been affected.
• School requirements should be interpreted using current CDPH guidance and any additional instructions issued by the applicable local health department.

Applied Biomedical Perspective

The renewed attention to TB in California highlights the continued need for accessible, timely, and reliable diagnostic strategies. Applied Biomedical remains focused on advancing point-of-care diagnostic technologies and supporting innovation that can strengthen infectious-disease detection, screening, and public health response.

As diagnostic science continues to evolve, new molecular and rapid-testing approaches may help complement established public health tools by improving access to actionable information closer to the point of care.

Sources and Further Information:

• California Department of Public Health – Tuberculosis in California: 2025 Snapshot
• San Francisco Department of Public Health – Archbishop Riordan High School TB outbreak overview (June 2026)
• California Department of Public Health – School Staff and Volunteer TB Risk Assessment
• Fresno County Department of Public Health – TB exposure at a Fresno County school (April 2026)
• County of San Diego – Tuberculosis Exposure Reported at Sunset Elementary School
• Los Angeles County Department of Public Health – TB Screening Guidance for Schools