A 34-year-old man with HIV infection presents with a 3-month history of progressively increasing skin lesions on his face, neck, and trunk. He reports no pain or pruritus. Physical examination shows dozens of 2–5 mm, flesh-colored, dome-shaped papules, many with a central dell (umbilication). There is no surrounding erythema. He says over-the-counter acne treatments have not helped. His temperature is 37.0°C (98.6°F). Laboratory studies show a CD4 count of 65 cells/mm³. Which of the following best explains the course of this patient’s skin condition?

(Choose the best answer.)