More than 100 students and staff members at Watkins Mill High School in Montgomery County are expected to undergo testing for tuberculosis Tuesday, after concerns about exposure to the disease.

In February, county health officials said an individual at the Gaithersburg school had contracted TB. Tuesday’s screening follows a waiting period of eight to 10 weeks, which allows any infection to be detectable, health officials said. The risk of infection to students and staff at the school is small, they said.

Transmission generally requires eight hours of close contact in a small room while an untreated patient is there, and it is typically not associated with more casual contact such as passing in a hallway or being together in the cafeteria, according to health officials.

The students and staff offered testing — 126 people — were in classes or after-school activities with the infected person from October 2013 to January, officials said. They are not required to participate in the testing, but health officials said most people who are offered such testing take advantage of it.

Tuberculosis usually affects the lungs and can include coughing, chest pain, weakness and weight loss. Without treatment, it can be fatal.

“There’s not a high risk that anyone contracted it, but it is possible, so you have to go through the process to make sure everyone is safe,” Montgomery schools spokesman Dana Tofig said.

Concerns about TB exposure result in school-based screenings once or twice a year, said Mary Anderson, a spokeswoman for the county Department of Health and Human Services.

Montgomery had 85 active cases of TB in 2012, according to the most recent state figures.

Last year, the Fairfax County Health Department investigated three confirmed TB cases at Robert E. Lee High School in Springfield, and the county offered free testing in June and August to more than 2,000 people, including students, faculty and support staff.

Of those tested, 235 were positive for latent TB infection, which cannot be spread. Fairfax found no active TB cases, said Glen Barbour, a spokesman for the county’s health department.

Those unable to attend the screening can be tested at a county health center or by private physicians. A positive test result requires a chest X-ray, but it only indicates exposure at some point, not active disease. All X-rays and treatment are free at the county’s Dennis Avenue center, officials said.