At San Antonio's largest homeless shelter, huge fans cool off the temporary residents. The courtyard can get crowded. One of the hundreds of nightly boarders is James Harrison. "I lost my apartment and had nowhere else to go," he explains.

Like most people at Haven for Hope, Harrison, who is 55, doesn't plan on staying long. But while he's here, he's taking advantage of some free medical testing — a screening for dormant tuberculosis.

"People don't even think about TB anymore because you don't see it anymore," Harrison says. "There's nothing that tells you until it's too late that it's there."

Differences between latent and active TB

Tuberculosis is an airborne bacterial infection that attacks the lungs and can be deadly. There's a common TB skin test, but the San Antonio health department says the skin test takes 48 to 72 hours to produce a result and is susceptible to false positives. A blood test is more accurate and requires only 24 hours to get results. A vial of blood can be tested to see if people are carrying TB without showing symptoms. That's called latent tuberculosis infection, a condition that puts them at much greater risk of developing active, contagious TB if they are exposed again.

"It goes into your lungs and usually it hides there dormant for years and years. Although it sounds very scary, it is completely treatable," says Dr. Barbara Taylor, an infectious disease specialist who is part of a program called Breathe Easy South Texas. BEST is an ambitious $2 million effort to test at-risk people in 20 Texas counties — an area larger than some entire states.

The Texas Department of State Health Services is teaming up with the San Antonio Metropolitan Health District, UT Health San Antonio and University Health System. They offer testing at places like shelters, diabetes clinics, and medical offices that treat mostly low-income patients.

"It's not a problem that's on the south side or east side. It's a problem all across Bexar County," says Tommy Camden, TB services manager with San Antonio's health department. He says tuberculosis it rears its ugly head in urban and rural communities.

"It doesn't care what color you are, how much money you make," he adds. "As long as you're breathing, you're susceptible to catching tuberculosis."

Still, some populations are at greater risk of carrying the TB bacterium: the homeless, IV drug abusers, people with diabetes and those born in some other countries. For most people who test positive, the diagnosis of latent TB comes as a surprise. But testing is easy.

A third of the world's population is infected

"We've got some huge challenges ahead of us," Camden says, because there is so much latent TB out there.

Texas, California, Florida and New York have the highest rates of tuberculosis in the U.S. Camden says he hopes those states can mimic the BEST program, which has screened 3,500 people a year. Roughly 9 to 10 percent were found to have latent TB.

"I am passionate about this because this condition can affect you when you least expect it," says nurse Diana Cavazos with University Health System. She says those who test positive are given X-rays and a 12-week course of antibiotics — even transportation to the appointments if they need it, free of charge.

"Testing, supplies, treatment, X-rays — it's completely covered," Cavazos explains.

It's covered by Medicaid. But future funding is a question mark. The threats in Washington, D.C., of cuts to Medicaid are creating uncertainty at precisely the time the testing program has plans to expand.

This story is part of NPR's reporting partnership with Texas Public Radio and Kaiser Health News.

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