Viruses are capable of causing a wide variety of disorders of the skin and mucous membranes. Viral-induced skin lesions include vesicles, pustules, papules, ulcers, and tumors. Cutaneous reaction patterns to viral infections most commonly appear as vesicles and bullae (herpes simplex and zoster virus infections), papulosquamous lesions (pityriasis rosea), or viral exanthems (discussed in Chapter 7: Viral and Bacterial Exanthems).

Certain viral infections, such as warts vary greatly in their gross clinical appearance despite all being caused by different subtypes of the same human papillomavirus (HPV). For example, warts may be papillomatous (common warts), threadlike (filiform warts), flat (planar warts), exuberant moist papules (condyloma acuminata), or develop into tumors (giant condyloma acuminatum of Buschke-Löwenstein). In contrast, lesions of molluscum contagiosum tend to be quite monomorphic and uniform in appearance and vary primarily by size.

The virus of varicella-zoster (VZV) may produce the clinical syndrome of either chickenpox or herpes zoster. Herpes simplex virus (HSV) may manifest as a local recurrence of vesicles on the skin or rarely, it can produce a more widespread illness such as herpetic encephalitis or Kaposi varicelliform eruption.