Thirty-one students at Hillside Intermediate School have tested positive for exposure to tuberculosis, but further tests are needed to determine how many are infected with the disease.

Thus far, there has been only one confirmed case of the disease at the school. Salt Lake City-County Health officials offered free tests last week after a Hillside student was diagnosed with the disease.Dr. Thomas Schlenker, health department executive director, said students exposed to tuberculosis will next undergo a chest X-ray.

"If there is any active disease, it will show up in a chest X-ray. In most cases the X-rays are clean, which means the individual has been exposed to TB but hasn't developed the disease," he said.

The disease is treated with oral antibiotics. Even if exposed to the disease, a healthy immune system usually keeps the disease in check, he said.

Tuberculosis is a lung ailment cause by airborne bacteria spread by sneezing and coughing.

The last time a Utah student is known to have contracted tuberculosis was in February 1996. About 60 students and teachers were tested at Davis High School, and those who tested positive were treated with antibiotics.