Charles County Schools sent a letter to parents to inform them that someone at La Plata High School had been diagnosed with tuberculosis (TB) disease.
Health officials are investigating. They have not said if a student or staff member was infected.
People who had prolonged exposure to the individual will be contacted by the health department with an opportunity to receive testing.
Tuberculosis is a bacterial illness that typically responds well to treatment. The rate here in the U.S. has declined dramatically and there is a vaccine to prevent infection.