A person at Commack High School has been diagnosed with tuberculosis, the district said Tuesday in a message posted on its website.
The district did not identify the infected person or say whether the person was a student or staff member.
The posting said the Suffolk County Department of Health notified the district "that an individual at Commack High School has been diagnosed with tuberculosis. The affected individual is presently receiving treatment and is not currently in attendance as a staff member or student. Therefore, there is no further risk of transmission."
Letters have been mailed to parents of all students and each staff member at the high school, the posting said. A separate letter was sent "to all students and staff who were identified as having been in close and prolonged contact with this individual," the posting said.
A call to Commack schools Superintendent Donald James was not immediately returned.
Dr. Shaheda Iftikhar, of the county health department's division of patient care services, said the county identified the infected person earlier this month and notified the school district "within 24 hours."
Citing privacy laws, Iftikhar said she could not offer any more information about the infected person.
The posting also said the health department would present information sessions for parents at 7 p.m. Thursday and Friday in the high school auditorium.
Iftikhar said the county has had 31 tuberculosis cases this year, including the Commack case. Last year, Suffolk County had 40 cases of the disease, according to county health records. Nassau County had 48 cases last year, according to the state health department.
The U.S. Centers for Disease Control and Prevention said tuberculosis is caused by a bacterium that usually targets the lungs but can attack any part of the body. The disease can be fatal if not treated properly and is "spread through the air from one person to another," the CDC said.