Review Question - QID 210537

A 22-year-old man presents to the emergency department with a sore throat. He says his symptoms have persisted for the past week and have become so severe that he can no longer eat food. The patient has no significant past medical history and is not taking any medications. He is a freshman in college and recently joined a fraternity. The patient drinks 4 to 5 drinks every day of the week and smokes marijuana. His temperature is 100°F (37.8°C), blood pressure is 117/68 mmHg, pulse is 90/min, respirations are 17/min, and oxygen saturation is 98% on room air. Physical exam is notable for the finding in Figure A. Bilateral symmetrical posterior cervical lymphadenopathy and splenomegaly are also noted. Which of the following is the best next step in management for the most likely diagnosis?