Review Question - QID 213757

A 24-year-old man is brought to the emergency department for shortness of breath and chest pain. His symptoms started 2 days ago without any clear precipitating factor and have progressively worsened. He reports some subjective fevers, chills, and diaphoresis today but denies any recent sick contacts, rhinorrhea, cough, sore throat, abdominal pain, or diarrhea. He just returned from a business trip from South Korea 2 days ago. Prior to this, he also had a root canal for a badly decayed molar tooth. Family history and past medical history were noncontributory. He is a regular IV drug user and his last use was 3 days ago. A physical examination demonstrates a patient in acute distress with rigors. The chest pain is not reproducible with palpation, S1/S2 heart sounds are present without any murmurs or gallops. There are faint inspiratory and expiratory wheezes bilaterally but the physical examination is otherwise unremarkable. What is the most likely cause of this patient’s condition?