Which viruses cause grouped blisters on a red base? | Fig. 24.2 A, Grouped vesicles limited to a dermatome in herpes zoster infection. B, Discrete palmar vesicle in epidemic hand, foot, and mouth syndrome. (Panel A courtesy of James E. Fitzpatrick, MD.) | Herpes simplex virus and varicella-zoster virus (Fig. 24-2A). |