A 52-year-old man undergoes elective open cholecystectomy for cholelithiasis. On postoperative day 5, he develops pain, swelling, and redness around the surgical wound. On examination, the structure marked **A** in the diagram—erythema extending more than 2 cm beyond the wound margin—is noted, along with surrounding warmth and induration. The patient is afebrile with a normal white blood cell count. Which of the following best describes the classification of this surgical site infection according to CDC criteria?