A 50-year-old man on ICU has a new onset seizure. EEG shows generalised periodic discharges (GPDs) at 1 Hz. He was admitted 5 days ago with confusion and fever. MRI shows temporal lobe hyperintensity bilaterally. CSF shows lymphocytic pleocytosis, elevated protein, normal glucose, and RBC count of 200/µL. What is the most likely diagnosis?