Viral Infections USMLE Step 1 Practice Question

A 64-year-old man with type 2 diabetes mellitus presents to the clinic with a 2-day history of severe burning pain along his right mid-thoracic region. He describes the pain as constant and radiating, with intensity 8/10. Yesterday, a painful vesicular rash appeared in the same dermatomal distribution. On examination, temperature is 37.5°C, and there are grouped fluid-filled vesicles with erythematous bases arranged in a unilateral band across the right T5-T6 dermatome. The vesicles are at various stages, with some already beginning to crust. There is no evidence of rash beyond the midline. Which of the following viruses is most likely responsible for this clinical presentation?