Some Cobb County high school students and staff members will be retested to determine if they contracted tuberculosis weeks after a student tested positive for the disease.

Back in September, testing was scheduled for students at two Cobb high schools after district officials learned a student may have contracted the disease over the summer. That student was attending Hillgrove High School this year, but was attending McEachern High in the spring.

Hillgrove High students who will have to have the skin test re-administered were sent home with information on Wednesday. Hillgrove Principal Christian Suttle explained the need for the retests in an email sent by the school’s Parent-Teacher-Student Association.

“Due to an extended incubation time of eight to ten weeks, the recommended CDC protocol is for anyone initially getting a negative skin test, to be retested for the disease,” Suttle said in the emailed message. “The Cobb County School District along with the Cobb Douglas Health Department will repeat the PPD skin test on students and staff who previously had a negative reading on their TB test.”

Tuberculosis, or TB, is caused by a bacterium that typically attacks the lungs, according to the Centers for Disease Control and Prevention. TB is spread through the air, but not through general contact with others, such as shaking hands, sharing food or drinks, or kissing, according to the CDC.