St. Louis Park High School will screen students and staff for tuberculosis after someone at the school tested positive for the disease.

The St. Louis Park School District mailed letters notifying families Wednesday about whether the Hennepin County Department of Health recommends their student be tested.

The district was first alerted in late November when the Health Department found that an individual at the high school had active tuberculosis. Tuberculosis, which affects the lungs, is one of a group of diseases closely monitored by the state because it is highly infectious and potentially fatal.

By that time, the individual was receiving care and did not pose a risk to anyone at the school. But the person had been in the school from September until November, before the diagnosis.

District officials said that privacy laws do not allow them to reveal whether the contagious individual was a student or staff member.

District Superintendent Rob Metz said in the letter that the Hennepin County Department of Health asked the district to delay notifying the community until the department could find out who needed to be tested.

The Health Department will test anyone who had any contact with the contagious person.

Free testing will take place on Jan. 30 and Jan. 31. Students who receive a letter saying they should be tested must return to school with a signed permission form before they can be tested. Students must return their signed form by Jan. 19. About 166 students will be tested, out of about 1,400 at the school, said Bill Belknap, spokesman for Hennepin County Department of Health.

According to that agency, it can take months for a case of tuberculosis to be found through testing. Students will be screened via a skin test.

"Although this is a unique situation for us, the Hennepin County Department of Health has dealt with similar situations on numerous occasions," Metz said in a letter to families. "We are working closely with them ... and are working to support our students and staff members in every way possible."