RACINE, Wis. (AP) -- The Racine United School District is reporting what's believed to be the district's first case of whooping cough.

A letter was sent home Tuesday with students at Horlick High School. In it, district officials say they received confirmation of a case of pertussis at the school.

District spokeswoman Stacy Tapp says the student returned to classes Monday after completing the required five-day course of antibiotics. She says the student went to the doctor during the Thanksgiving break last week and began treatment.

Tapp declined to comment on the student's age, grade level and gender.

Whooping cough is a contagious bacterial infection that affects the respiratory system.

The Journal Times reports officials with the city health department and Wisconsin Department of Health Services were not immediately available for comment.

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