California tuberculosis cases reach 12-year high as CDC reports new outbreak details

California reported 2,150 tuberculosis cases in 2025, reaching a 12-year high with a rate of 5.4 per 100,000 people—nearly double the national rate of 3 per 100,000. The CDC documented a dramatic increase in large TB outbreaks nationwide, from 24 between 2014-2016 to 50 between 2017-2023, with 79% of recent outbreak cases affecting U.S.-born individuals despite most TB cases nationally occurring in foreign-born populations. Risk factors driving outbreaks include homelessness, substance abuse, incarceration history, and malnutrition, with two-thirds of outbreaks linked to family or social networks. A notable outbreak at Archbishop Riordan High School in San Francisco resulted in at least three active cases and over 200 latent infections, illustrating how TB spreads effectively in group settings.

Rising tuberculosis cases in California and nationwide outbreak trends

• ▪Large tuberculosis outbreaks are defined by the U.S. Centers for Disease Control and Prevention as 10 or more active TB cases
• ▪The national tuberculosis incidence rate in the United States is three per 100,000 people
• ▪There were 24 large tuberculosis outbreaks nationwide in the United States between 2014 and 2016
• ▪California reported 2,150 tuberculosis cases in 2025, a 12-year high
• ▪About 13% of people with tuberculosis in California died in 2023
• ▪California's tuberculosis rate was 5.4 per 100,000 people in 2025

Demographics and risk factors of TB outbreak populations

• ▪About two-thirds of large tuberculosis outbreaks between 2017 and 2023 were associated with family or social networks
• ▪Homelessness is a risk factor for tuberculosis in the United States
• ▪79% of people affected by large tuberculosis outbreaks between 2017 and 2023 were born domestically in the United States
• ▪Individuals affected by large tuberculosis outbreaks were more likely to have substance abuse issues
• ▪Most people diagnosed with tuberculosis in the United States are foreign-born

TB transmission patterns and recent outbreak examples

• ▪A tuberculosis outbreak at Archbishop Riordan High School in San Francisco saw its first positive test for active TB in November
• ▪Latent tuberculosis will not cause symptoms or spread to others
• ▪Latent tuberculosis can turn into active tuberculosis at any time
• ▪Active tuberculosis can cause symptoms and be transmitted to others
• ▪The tuberculosis outbreak at Archbishop Riordan High School in San Francisco resulted in more than 200 latent TB cases

Perspective of Public health officials

• ▪California's tuberculosis rate of 5.4 per 100,000 people indicates substantially higher disease burden than the national average
• ▪The shift in tuberculosis outbreak demographics toward domestically-born individuals represents a change in disease transmission patterns in the United States

Perspective of Archbishop Riordan High School community

• ▪The Archbishop Riordan High School tuberculosis outbreak required mass screening of students and staff beginning in November 2024
• ▪More than 200 individuals at Archbishop Riordan High School required treatment for latent tuberculosis infection following the outbreak