<s>[INST] A 30-year-old woman comes to the physician with complaints of fever and a sore throat. She reports that she was diagnosed with streptococcal pharyngitis 2 weeks ago, and was prescribed a course of penicillin. She says that she took the penicillin as directed, and finished the full course. She now reports a fever of 102.5F, a sore throat, and difficulty swallowing. Her physical exam is notable for exudative tonsillitis and bilateral cervical lymphadenopathy. 

What is the most likely cause of her current symptoms?[/INST]