Q. 54 year-old woman is brought to the ER after being observed to have tonic-clonic convulsions in a village market. She lost consciousness after the convulsions. EMS noted that she had lacerated her tongue and lost control of her bladder. As she gradually regains consciousness, she reports that she has been having strange smells and has been experiencing episodes of Deja Vu fairly frequently over the past several weeks. She has had an uneventful medical history. No family history of seizures. She was born in Kansas but moved to Idaho 10 years prior. She has never left the United States. She has a 50 pack-year history of smoking. Drinks alcohol socially and denies any use of illicit drugs. Her exam is fairly unremarkable. Temperature is 36.7 (98.7 F), Blood Pressure is 130/80, Heart Rate is 72 beats/minute. Neurological examination is notable for her lethargic status and asymmetrically brisk muscle stretch reflexes with pathologic reflexes observed. Cardiopulmonary auscultation is normal. No masses present on abdominal examination. CMP, CBC, and urinalysis are all normal. Non-contrast head CT demonstrates multiple areas of abnormal hypodensities. MRI of the brain with and without contrast demonstrates numerous (more than 15) small, circumscribed lesions with surrounding edema in the fronto-temporo-parietal lobes. HIV testing is normal. Which of the following is the most likely cause of this patient's seizure?