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'This is a big outbreak': Nearly 1 in 5 affected by TB at SF school

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New data shows 18%, or nearly 1 in 5, of tested students and staff at 
Archbishop Riordan High School in San Francisco were diagnosed with either 
latent or active tuberculosis during an outbreak that started in November. 

New testing is scheduled to start today. 

In total, 96% of the school community was tested, seven people were 
diagnosed with active cases during the course of the outbreak and 241 
latent cases were reported, according to data released by the San 
Francisco Department of Public Health on April 27 to the school community. 

In February, four active cases and three suspected active cases were 
reported. The latest numbers reflect the suspected cases were confirmed to 
be active TB. The entire school community went through another round of TB 
testing in March. 

“Data from the March 2026 round of testing indicate a strong reduction in 
transmission,” the department said in an emailed statement to SFGATE 
Wednesday.   

The department also stressed that “repeat mass testing at the school is no 
longer required.” They said the new testing is “out of an abundance of 
caution” and only for those who had a recent exposure to a confirmed case 
or were part of a “small group of individuals with new latent TB cases” 
found during the March testing. 

Dr. Monica Gandhi, an infectious disease expert at UC San Francisco, 
explained that TB is a slow-growing disease, which means testing may not 
start for eight to 10 weeks after an exposure to active TB. 

“Every time there’s an active case, you start the clock from there in 
terms of rounds of testing,” she told SFGATE in a phone call. “If that 
person was at school, then everyone around them needs contact tracing and 
testing again.”

Gandhi noted that the California Department of Public Health defines a TB 
cluster as being four or more active cases.

“This is a big outbreak,” she told SFGATE of the seven active cases 
reported.

Tuberculosis, an ancient bacterial disease that dates back 9,000 years, 
can be either active or latent, according to the U.S. Centers for Disease 
Control and Prevention. When it’s active, the disease can be transmitted 
and also cause symptoms like cough, fever and weight loss. In latent form, 
it won’t cause symptoms or be transmitted. However, the disease can turn 
into an active case at any time, even decades after the initial infection.

Both active and latent TB can be treated with an antibiotic treatment that 
typically takes months.

While latent TB doesn’t result in symptoms, Gandhi said it was unusual to 
see such a high percentage of the school population be diagnosed with the 
condition.

“Kids in this country do not have latent TB like that,” she said. “Those 
kind of numbers, of 20% having latent TB, are in low-income countries.” 

Requests for further comment from Archbishop Riordan High School were not 
answered by the time of publication.

The  California Department of Public Health noted that the last time an 
infectious person was on campus was Feb. 19. As of March 9, only students 
who had been tested for TB and “have TB clearance on file with the school” 
are allowed on campus or at off-campus school events. The department said 
95% of those diagnosed at the school with latent TB are undergoing or have 
finished treatment, and all of those who had been diagnosed with active TB 
were being treated.

Tuberculosis remains a problem for California, where cases hit a 12-year 
high in 2025 with 2,150 reported. The state also had a “substantially 
higher” rate of disease in 2025 than the U.S. overall, the department 
said, with 5.4 infections per 100,000 people compared with about 3 per 
100,000 nationwide.

https://www.sfgate.com/bayarea/article/tb-sf-private-school-22244806.php

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'This is a big outbreak': Nearly 1 in 5 affected by TB at SF school Nincompoop Newsom <sanctuary@states.rus> - 2026-05-07 09:39 +0000
  Re: 'This is a big outbreak': Nearly 1 in 5 affected by TB at SF school hailtrump@gmail.com - 2026-05-09 19:50 +0000

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