A 32-year-old man from Mumbai presents to the STI clinic with a 3-week history of fever, generalized lymphadenopathy, and a maculopapular rash over his trunk and palms. He reports unprotected sexual contact with multiple partners over the past 6 months. His CD4 count is 450 cells/μL, and HIV serology (ELISA) is negative, but HIV RNA (viral load) is 85,000 copies/mL. What is the most likely clinical stage of HIV infection in this patient?