A person at Renton High School was recently diagnosed with active tuberculosis, prompting King County health officials to host a free screening this week at the high school.

According to district Spokesman Randy Matheson, Public Health – Seattle &King County officials contacted the district late on Oct. 28 to notify them of the case. Matheson said the individual, whose name is not being released due to state law, was diagnosed after visiting their personal doctor, who passed the information on to county officials. It is unknown if the person is a student or staff member.

TB is an infectious disease caused by bacteria that are passed from person to person through the air, but it’s much harder to spread TB than the cold or flu.

TB usually affects the lungs, but can affect lymph nodes, bones, joints, and other parts of the body. A person with active TB in the lungs can spread the disease by coughing or sneezing. In King County, 98 new cases of TB disease were reported in 2015. On average, two cases of TB disease are diagnosed in King County each week.

The person with active TB disease is currently receiving treatment, and is not currently a risk for infecting others, according to the county. Most cases of TB are readily treatable with antibiotics that are commonly available. To become cured, a patient must complete the entire treatment, even after the patient is no longer infectious. If the treatment is interrupted before the bacteria are completely eliminated, TB can develop drug resistance and become much harder to treat.

School and health department officials have met several times and out of what Matheson called an “abundance of caution” have notified 115 students that they may have come in contact with the disease in a classroom and the school and that they are available to take the free screening Thursday at the school. Matheson said about half of those contacted have returned forms indicating they will be screened.

“The likelihood that anyone is infected by this person is extremely low,” Matheson said.

People at Renton High School who are identified through the blood test to be infected with latent TB may be recommended for treatment, so that they do not develop the disease in the future.

Unlike active TB disease, people with latent (or dormant) TB infection can’t spread it to others and are not ill with the disease. Approximately 100,000 people in King County have latent TB infection. While they aren’t contagious now, they could potentially have active TB in the future and also infect others.

Approximately 5 percent of newly infected contacts of a person with active TB develop active TB disease themselves within two years. An additional 5 percent become ill at some point over the remainder of their lives. Ninety percent of people with latent TB infection never develop active TB disease.

Matheson said the district would continue to work with the county to monitor the results of this week’s tests and would follow up with any students or staff who test positive for the disease.

Reach Editor Brian Beckley at 425-336-4959.