Why TB cases are rising in California after decades of decline

Once known as consumption, the disease that killed Eleanor Roosevelt, Frederic Chopin and all five of the sisters Bronte, tuberculosis is often viewed as a bygone threat.

But there is an uptick in new California illnesses after years of decline, with the number of cases in the Golden State increasing from 1,704 in 2020 to 1,848 in 2022.

Santa Clara County has released new data showing a 19% jump in cases from 2022 to 2023. Increased cases also were reported in Alameda, Contra Costa and San Francisco counties.

The rebound does not represent a dangerous outbreak but rather the scattered re-emergence of a hidden health risk that is being detected in the wake of the COVID pandemic, according to health experts. Diagnoses may have been missed, misdiagnosed or delayed, they said.

"This is a 'slow burn' of an age-old disease that's now increasing, probably because we let our guard down and didn't emphasize the need for prevention of progression" from latent illness to active tuberculosis, said Dr. Priya Shete, associate professor of medicine and epidemiology at UC San Francisco.

Greg Lyon, 78, of San Francisco, was startled by his diagnosis. In otherwise good health, he experienced mysterious fevers and extreme fatigue while recovering from a normal bout of COVID.

"In my mind, it was relegated to a medieval kind of disease," said Lyon, whose infection was likely acquired while traveling years ago in Guatemala, then lay dormant for decades. His doctors suggest that COVID may have perturbed his immune system.

"I realized it existed, of course, but I just never knew of anybody who had it," said Lyon, whose infection was successfully treated.

TB begins with a mild fever and malaise, followed by a painful cough and shortness of breath.

An ancient foe, the bacterial infection continues to rage, virtually unchecked, throughout the developing world. It's the second-most deadly infectious disease in the world, following COVID, killing 1.2 million people each year.

In the United States, "TB is treatable. TB is preventable. But you have to get tested," said Dr. Ann Loeffler, assistant health officer and TB Controller for the Public Health Department of Santa Clara County, where cases jumped from 141 in 2022 to 168 in 2023.

Only a small proportion of people who are infected with TB will develop active disease. People with latent TB infection don't feel sick.

The bacteria spreads through the air when infected people cough, sneeze or spit. The infection prospers in crowds, spreading to people in close reach. Nearly a dozen tuberculosis cases—all genetically linked—were traced to California Grand Casino in Pacheco over the past five years, according to Contra Costa Health.

People who are infected but not ill with the disease cannot transmit it.

Most cases emerge in people who were born or spent extensive time in high-risk countries, primarily Mexico, Central America, the Philippines, Vietnam and China.

Certain conditions, such as diabetes or a weakened immune system, may boost the chance that an infected person will develop the disease.

"If you spent a lot of time in an area where TB is very common" or have risk factors that suppress your immune system, "then you should be talking to your doctor about under what circumstances you should be tested," said Loeffler.

A combination of factors may be driving the current increase in diagnoses, said experts.

During the pandemic, testing and treatment was deferred, said UCSF's Shete. That's because people who had a cough may not have sought care—or, if they did, may have simply assumed it was COVID.

"They went along with their symptoms for awhile until they became progressively more and more ill," she said. "What we're seeing now might be the progression of that active disease that was never identified earlier. Now they're presenting for care at a time when their symptoms are more severe."

And providers are starting to consider other infections, not just COVID, added Loeffler.

Perhaps there is an increase in transmission because fewer people are wearing masks, she added. "People are out in the world more, and mixing."

A similar pattern has been seen globally, said Dr. Jason Andrews, an infectious disease expert at Stanford Medicine. Some nations reported up to a 30% decline in TB cases during the pandemic, then a recent rebound.

"This is something that we've seen all over" as the COVID-19 pandemic set back the fight against other global scourges, he said. "We've started to identify people who were not diagnosed in 2020 and 2021—and because they were diagnosed late, there was probably more spread in the community."

While drug-resistant TB is a growing global threat, it represents a small percentage of cases in the U.S. and is treatable with existing medicines, said Andrews.

The development of improved diagnostic technologies is shortening testing times from weeks to hours. Treatment for non-drug-resistant TB also has gotten easier, shortened from two years in the 1980s down to four months today. At least 17 vaccine candidates are now in the testing phase.

After months of treatment with four different antibiotics, Lyon is making a slow but steady recovery.

"I'm still not back to my normal self. Some days I feel just generally crappy," he said. "But I'm walking a mile or two every day. I'm on the upward side."

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