A high school in Sussex County has announced that a “member of our community” has been diagnosed with pertussis, more commonly known as whooping cough. The letter from High Point Point Regional High School on Thursday did not specify whether the case involves a student, teacher or staff member. Pertussis is a highly contagious respiratory tract infection, typically spread by sneezing or coughing. It can result in serious illness in people of all ages and can be life-threatening, especially in babies, according to the Centers for Disease Control and Prevention. “The Department of Public Health …