An Alabama school district has announced the closure of all of its schools due to a flu outbreak among students and staff.

Opp City Schools in Covington County is closing its three schools for the rest of the week, Superintendent Michael Smithart wrote in a Facebook post on Wednesday. The official said the district was seeing “a very significant” increase in the number of diagnosed flu cases and the number of students and staff members presenting flu-like symptoms.

All facilities were closed, and all on-campus extracurricular activities were canceled, the post said. Students will still be required to complete online lessons, the district confirmed.

Classes were set to resume on Feb. 3.

Lamar County Schools in west Alabama also closed on Wednesday for the rest of the week after 400 out of 700 students at one school failed to attend class on Tuesday amid a flue outbreak there, the superintendent told news outlets.

More than half of influenza-positive test results from public health laboratories this season were in children and adults younger than 25 years old, The Dothan Eagle reported, citing Alabama Department of Public Health data.