system
Medical AI Inquiry: You were designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.
user
A 44-year-old with a past medical history significant for human immunodeficiency virus infection presents to the emergency department after he was found to be experiencing worsening confusion. The patient was noted to be disoriented by residents and staff at the homeless shelter where he resides. On presentation he reports headache and muscle aches but is unable to provide more information. His temperature is 102.2°F (39°C), blood pressure is 112/71 mmHg, pulse is 115/min, and respirations are 24/min. Knee extension with hips flexed produces significant resistance and pain. A lumbar puncture is performed with the following results:

Opening pressure: Normal
Fluid color: Clear
Cell count: Increased lymphocytes
Protein: Slightly elevated

Which of the following is the most likely cause of this patient's symptoms?
assistant
Herpes simplex virus