Mr. B is a 35-year-old man with HIV who is currently taking indinavir 800 mg tid, emtricitabine 200mg/tenofovir 300 mg daily, ritonavir 100 mg daily, trazodone 100 mg q hs, and buspirone 15 mg tid. His primary care provider started ketoconazole 200 mg qd one week ago. The PMHNP decides to start sertraline (Zoloft) 50 mg one po qd for depression. Mr. B returns to see his primary care provider 4 days later with fever, chills, diarrhea, muscle aches, and confusion. What is the most likely cause of his symptoms?