America’s tuberculosis (TB) capital has recorded its highest number of infections in more than a decade, a report shows.
Latest data from California revealed the state registered 2,150 cases in 2025, marking its highest tally since 2013, or in 12 years, and a two percent rise on the year before.
The state, which recorded the most infections in the nation, also had a TB infection rate that was nearly double the national average.
About 13 percent of patients infected with TB, or 279 individuals, died last year.
It comes after the US recorded more than 10,000 TB cases in 2024 – which marked the highest tally since 2011. In that year, infections rose in 80 percent of US states.
Experts have blamed the surge on distrust of doctors forged by the Covid pandemic that has led fewer people to seek treatment until the later stages, when a TB infection may have progressed into an active disease.
Last week, officials in California raised the alarm over a TB outbreak at an exclusive $30,000-per-year private school in San Francisco that had led to more than 241 individuals being exposed to the disease.
TB is caused by a bacteria – mycobacterium tuberculosis – that is easily spread through coughs and sneezes.
TB cases have hit a 12–year high in California (stock image)
The ‘Victorian era’ disease is considered to be one of the deadliest in the world, as estimates suggest more than 50 percent of patients die from the disease if they do not receive treatment. Children, especially those under five, are most at risk.
In the early stages, patients suffer from a persistent cough and coughing up blood. Later, they may also develop breathing difficulties and lung damage, which can be fatal. The disease may also spread to other organs, including the brain or spinal cord.
Doctors typically treat the infection with antibiotics, although some strains of TB are now emerging that are resistant to some of these drugs.
A vaccine to prevent infections is available, but it has never been routinely offered in the US because of the country’s low rate of TB cases.
The new figures were revealed in a report released by the California Department of Public Health, which was recently covered in local media.
All the patients had active infections, or cases where the bacteria were causing symptoms and an infection in the body.
Some patients are diagnosed with latent TB, when the disease is detected in the body but is being suppressed by the immune system.
A total of 279 people died from the disease in California last year, or 13 percent of the patients. Of the fatalities, 24 percent did not receive treatment.
The state had an annual incidence rate of 5.4 cases per 100,000 people – nearly double the national average of three cases per 100,000.
Forty-five of the state’s 61 local health authorities reported at least one case of TB.
About 83 percent of the cases were due to latent infections progressing to active infections, officials said, suggesting they may have been prevented with testing and treatment.
And about seven percent of cases were in people who had arrived in the state with the disease, and 10 percent resulted from another recent transmission.
Californian health officials said their state had recorded about 2,000 to 2,100 infections every year since 2013, but that these dipped during the Covid pandemic.
This marked an about 60 percent drop from the peak of infections in 1992, when there were 5,300 recorded in the state. They were driven down as part of a major public health effort.
Data on the number of infections that led to hospitalization was not provided. It was also not clear how many infections California had recorded this year.
Dr Martin Willis, the former public health officer for Marin County, on the outskirts of California, told SFGate that TB ‘thrives’ when individuals lose access to healthcare.
‘Those are the people who, when they have latent disease, it’s not detected, it’s not treated, and they become active, and then they are infecting others,’ he said.
Provisional data showed that TB cases dropped one percent in the US last year compared to the previous period, but remained above 2011 levels, the previous high in infections.
In the outbreak at the California school that is ongoing, seven pupils have an active infection and 241 have a latent infection or are carrying the bacteria.
‘This is a big outbreak,’ Dr Monica Gandhi, an infectious disease expert at the University of California San Francisco, told SFGATE.
She also noted that while latent TB does not cause symptoms, it is unusual to see such a high percentage of the school population diagnosed with the condition.
‘Kids in this country do not have latent TB like that,’ she said. ‘Those kind of numbers, of 20 percent having latent TB, are in low–income countries.’
TB infects a few thousand Americans every year and kills around 500, but the threat is much more prevalent in developing countries. Worldwide TB kills 1.2 million people each year.
