Roseola Infantum (Exanthem Subitum; Pseudorubella) By Brenda L Tesini, MD, University of Rochester School of Medicine and Dentistry Reviewed / Revised May 2023 View Patient Education Symptoms and Signs Diagnosis Treatment Topic Resources Roseola Infantum (Rash) Roseola infantum is an infection of infants or very young children caused by human herpesvirus 6B (HHV-6B) or, less commonly, HHV-7.