Health Update: Tuberculosis (TB) Outbreak at a Local High School – Clinical Evaluation and Reporting

The San Francisco Department of Public Health (SFDPH) is issuing this health update with updated recommendations to health care providers regarding a tuberculosis (TB) outbreak associated with Archbishop Riordan High School, including the next steps in evaluation, testing, and reporting for exposed students and staff after completion of the first round of all-school testing. This updates the information previously shared in the health advisory released January 29, 2026 (Tuberculosis (TB) Outbreak at a Local High School – Clinical Evaluation and Reporting).

Situational Update

SFDPH continues to conduct a large-scale contact investigation of a TB outbreak at Archbishop Riordan High School (ARHS) in San Francisco. To date, four cases of active TB disease have been laboratory-confirmed in persons associated with ARHS since November 2025. There are also three suspected cases of active TB for whom final culture results are pending. All confirmed or suspected cases of active TB disease are on treatment with health department monitoring of directly observed therapy. SFDPH has received test results for a total of 1359 ARHS students and staff (96% of the school population) as of February 24, 2026. Among these 1359 individuals, 227 (17%) had a positive TB test (IGRA or skin test). Of those, there are 207 individuals with confirmed latent TB infection (LTBI), and x-ray results to rule out active TB are in process for the remaining individuals with a positive TB test. Efforts are underway to ensure preventive treatment for all individuals with LTBI. This health update aims to notify local pediatric, urgent care and primary care providers of follow-up actions to take to prevent TB in this highly exposed population. At this time, risk to the general population is low, so these measures are not needed for persons who are not connected to the AHRS outbreak.

To protect the school community, staff and students of ARHS have been instructed to stay home if ill and seek medical clearance to return. Additionally, repeat TB evaluation is required for all students and staff affiliated with the school during the week of March 16, 2026, regardless of prior test results or the presence of symptoms. For convenience and ease of reporting, all students and staff are encouraged to participate in on-campus mass screening planned for that week at the school. For students and staff who opt not to be tested during the on-campus screening, community health care providers play a critical role in timely identification of active TB disease, appropriate evaluation for LTBI, clearance for school and work attendance, and prompt reporting to public health authorities. Additional assessments may be required in the future until the outbreak is resolved.

At this time, the TB exposure risk to the general population is low, and these preventive actions should be focused on ARHS students and staff.

Background

Active TB disease is a mycobacterial illness that most often affects the lungs, and usually causes symptoms such as prolonged cough, hemoptysis, fever, fatigue and weight loss. In the active stage, TB is a serious illness that can be transmitted to others and illness can range from mild to life-threatening. Abnormalities are almost always apparent on chest Xray (CXR) of patients with active TB of the lung. LTBI has no symptoms and the CXR is typically normal. In the latent stage, TB is not contagious but can develop into active TB in 5-10% of those with the infection. 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. Because of this risk, diagnosis and treatment of LTBI is critical to prevent the development and spread of active TB disease.

Actions requested of clinicians regarding ARHS students and staff:

Please refer to our workflow diagram: sf.gov/TB

TB evaluation is required for all students and staff of Archbishop Riordan High School. In addition to the school-based exposure, assess for additional epidemiologic or medical risk factors for progression to TB disease, including:

• Current or planned immunosuppression (e.g., HIV infection, organ transplant, TNF-alpha antagonists, systemic steroids, or other immunosuppressive medications)
  • A list of some commonly used biologics which may place patients at risk of more severe disease can be found on: TB Risks and Targeted Immunologics
• Birth, travel, or residence in a country with elevated TB rates (includes all countries outside the United States, Canada, Australia, New Zealand, and western or northern Europe)
• Close contact to a confirmed or suspected TB case
• Congregate living current or past, in a shelter, jail etc.

Symptom review and assessment of adherence to treatment for either latent TB infection (LTBI) or empiric LTBI treatment (i.e. window period prophylaxis (WPP)) is recommended when applicable. Good adherence is defined as taking ≥85% of all prescribed doses.

If there are concerns for TB symptoms or poor adherence to treatment, patients should undergo a focused exam for lymphadenopathy, a CXR, and have a repeat TB blood test with interferon gamma release assay (IGRA) if previously negative.

If the radiology report is concerning for active TB, consult the SF TB Clinic and if available, pediatric infectious disease.

Required Evaluation of All ARHS Students and Staff during the week of March 16, 2026

Symptom Review

Assess for symptoms consistent with active TB disease, including:

• Cough lasting >3 weeks
• Coughing up blood (hemoptysis)
• Fever
• Fatigue
• Unintentional weight loss or concerns about appropriate growth and development
• Night sweats

Focused Physical Exam

A focused physical exam should include assessment for cervical, supraclavicular and axillary lymphadenopathy. This should be performed for all persons with newly positive IGRA or who are not taking or are poorly adherent to LTBI treatment or WPP/empiric LTBI treatment, if applicable. On physical exam, TB adenopathy is predominantly cervical, (followed by supraclavicular and rarely axillary), usually unilateral, painless, and can be fluctuant, matted or associated with a draining sinus.

Test for TB infection in those with prior negative TB test only

• IGRA (TB blood test) strongly preferred
• TST may be used if IGRA not feasible; please note that definitions of a positive TST test cutoff varies depending on risk factors (use ≥ 5 mm for all individuals in this outbreak setting).

When to obtain a CXR (2 view PA and lateral):

• One or more symptoms suggestive of active TB disease; OR
• Conversion to positive TB test (newly positive on this round of testing); OR
• LTBI diagnosis but not started on or not adherent to a full course of treatment; OR
• Immunosuppression and not taking WPP/empiric LTBI treatment

Interpretation & Next Steps Based on Prior Testing:

1. IGRA/TST negative with no prior CXR and/or prior normal CXR
   1. Symptom review
      1. If negative, repeat IGRA/TST
   2. If TB symptoms present, repeat IGRA/TST, perform focused physical exam for lymphadenopathy and obtain 2-view CXR
      1. If physical exam and CXR normal → treat for LTBI
      2. If physical exam and/or CXR abnormal → isolate and consult SF TB Clinic (and pediatric ID specialist as appropriate)
2. LTBI diagnosis, on treatment or completed treatment
   1. Monthly symptom review + adherence check (≥85% doses taken)
   2. ii. Continue LTBI treatment until completed
3. LTBI diagnosis, NOT taking or non-adherent to LTBI treatment (<85% doses)
   1. Symptom review + focused physical exam for lymphadenopathy + 2-view CXR
      1. If physical exam and CXR normal→ strongly encourage LTBI treatment
      2. If physical exam and/or CXR abnormal → isolate and consult SF TB Clinic (and pediatric ID specialist as appropriate)

Special Population: Immunocompromised Patients

1. Previous IGRA/TST and CXR negative, ON window period prophylaxis/empiric LTBI treatment
   1. Symptom review and monthly adherence check (confirm ≥85% doses taken)
   2. Repeat IGRA if previously negative
      1. If no symptoms, good adherence and IGRA negative
         1. Continue window prophylaxis/empiric LTBI treatment
         2. Await further guidance from SFDPH about when to stop
      2. If symptomatic or adherence concerns → obtain physical exam and 2-view CXR
         1. If physical exam and CXR normal → strongly encourage adherence to window prophylaxis/empiric LTBI treatment
         2. If physical exam and/or CXR abnormal → isolate and consult SF TB Clinic (and Peds ID as appropriate)
2. Previous IGRA/TST and CXR negative, NOT on window period prophylaxis/empiric LTBI treatment
   1. Symptom review + focused physical exam for lymphadenopathy + 2-view CXR
   2. Repeat IGRA
      1. If physical exam and CXR normal → strongly encourage starting WPP/empiric LTBI treatment (consult SF TB Clinic)
      2. If physical exam and CXR abnormal → isolate and consult SF TB Clinic (and Peds ID as appropriate)

Treatment to prevent active TB disease

• Individuals with a positive IGRA test and normal 2 view CXR have LTBI. Persons with LTBI are strongly recommended to start TB preventive treatment once active TB disease has been excluded.
• Immune suppressed individuals with a normal CXR should initiate WPP/empiric LTBI treatment until the outbreak is determined by SFDPH to be over. The regimen normally used for WPP is the same for LTBI treatment. A detailed guidance document can be downloaded from this link to the UCSF Curry Center Pediatric Tuberculosis: An Online Presentation and Resources. Consult the San Francisco TB Clinic with questions.
• The most commonly prescribed LTBI regimen is rifampin, dosed at 600 mg daily for 4 months. Details about rifampin dosing in adults and children and an overview of other recommended regimens can be found on the CDC website. Rifampin induces cytochrome P450 isoenzymes (CYP) and some drug transporters, such as P-glycoprotein, impacting co-administered drug levels. Hormonal contraceptive efficacy may be reduced – a backup barrier method should be used while on rifampin. An overview of management of important drug-drug interactions is available from CDPH and the UCSF Curry International TB Center.
• Document treatment decision in the medical record and on the school form
• The highest-risk period for development of active TB disease is within the first 2 years after acquiring infection, with highest risk in the earlier months. Identified close contacts who decline LTBI treatment should be monitored with serial CXRs at least every 6 months for 2 years for early detection of progression to active TB disease. A CXR may be required more often in the setting of outbreak mitigation

Complete required school clearance form for all students and staff

For all evaluated individuals, complete the required school form and provide it to the patient for use in school TB clearance portal.

Report all results to SFDPH via Confidential Morbidity Report (CMR)

• Report outcomes for all screened individuals, even if they have only negative results
• Include supporting documentation: TB test results, CXR report, progress note with symptom review, physical exam and documentation of treatment
• Include in remarks section: Archbishop Riordan High School Outbreak screening

Call urgently to report suspected active TB disease

• Individuals with the following should be considered to have suspected or probable active TB disease:
  • Signs or symptoms of active TB disease AND
    • Immune suppression OR
    • Radiographic imaging suggestive of active TB

Suspected or confirmed active TB disease should be reported to SFDPH and are required by Title 17, California Code of Regulations (CCR) to be reported to the local health department of the patient’s county of residence within one working day. To report active TB disease to SFDPH, call (628) 206-3398 to make an initial report. Detailed reporting instructions can be found on our website.

Additional resources:

TB Outbreak Update presentation to San Francisco Health Commission 3/2/2026:

TB Reporting in San Francisco

Preventing TB Disease in 4 Steps (CTCA 5/2025)

Latent Tuberculosis Infection: A Guide for Primary Health Care Providers (CDC 2020)

Video provider training and infographic for this outbreak response are in development and will be available at sf.gov/TB.

Contact information

Susannah Graves, MD, MPH
Director, Tuberculosis Branch
San Francisco Tuberculosis Clinic
Phone: 628-206-8524 | Fax: 628-206-4565 | SF.gov/TB

View or sign up for SFDPH Health Alerts, Advisories, and Updates at sf.gov/healthalerts