Outbreaks Of Highly Contagious Disease Reach Record High In CA

SAN FRANCISCO, CA — Health officials are sounding the alarm on an unexpected surge in Tuberculosis cases in California revealed in a new report that shows more cases in the state are eclipsing the national average.

California set a new record after reporting more than 2,150 TB cases in 2025, the highest in 12 years. The national incidence rate of Tuberculosis is three per 100,000, California’s rate was nearly twice as high with 5.4 per 100,000 last year, according to a report released in March.

A report from the U.S. Centers for Disease Control and Prevention (CDC) showed there were 50 large Tuberculosis outbreaks between 2017 and 2023. The CDC defines large outbreaks as 10 or more active TB cases within a 3-year period. The authors analyzed 1,092 TB cases identified in 23 states.

The report was published last week in the Morbidity and Mortality Weekly Report.

The CDC study also found that 79 percent of TB cases tied to large outbreaks between 2017 and 2023 were people born in the U.S.

Among the 50 large outbreaks in the U.S., 68 percent were primarily associated with family or social networks, and 26 percent were primarily associated with congregate settings, according to the study.

The study also indicated people with TB were more likely to be abusing drugs.

Though treatable, Tuberculosis is potentially fatal and highly contagious. In 2023, the most recent reported year with complete data, the California Department of Public Health reported about 13 percent of TB cases were fatal.

Data shows the rate of TB infections in California continues to rise compared to national trends.

A Bay Area high school was scheduled to undergo additional testing on Wednesday after about 18 percent of students and staff were diagnosed with latent or active tuberculosis from an outbreak first reported in November.

Officials reported on April 27 that 96 percent of students and staff at Archbishop Riordan High School in San Francisco were tested. Seven people were diagnosed with active TB amid the outbreak and 241 latent cases were reported, according to the San Francisco Department of Public Health.

In February, SFDPH reported four active cases and three suspected active cases.

"Data from the March 2026 round of testing indicate a strong reduction in transmission," the SFDPH told SFGate.

SFDPH said the latest round of testing is out of precaution and "repeat mass testing at the school is no longer required," the SFGate reported.

Dr. Monica Gandhi, an infectious disease expert at University of California, San Francisco, said California has experienced an increase in Tuberculosis cases for several reasons, including the state's higher rate of housing insecurity, substance use, immigration, and incarceration in the state, which are all risk factors for TB.

"TB is generally a disease of poverty and is associated with concomitant social determinants of health, like unstable housing or minority status in the U.S., and these same factors affect TB rates in California," said Dr. Gandhi.

"I am concerned that with the deepening disparities between rich and poor in this country created by the current administration that we will see even higher rates of TB in the next few years in this country and state," she added.

The CDC study's authors said preventing and controlling outbreaks will require national genomic surveillance, as well as state and local TB programs.

"Outbreak prevention and response strategies must also overcome barriers to diagnosis and treatment associated with homelessness and substance use," said the study's authors.

"In addition, there is a need to build trust with affected persons and communities directly and through partnerships with local organizations and service providers. In congregate settings, maintaining procedures to promptly identify and isolate persons with infectious TB is critical for preventing TB outbreaks."