Fever stops and rash begins is diagnostic of –

Roseola infantum (Sixth disease or exanthem septum) It is caused by human herpesvirus-6 (HSV-6) Similar illness is caused by Parvovirus B-19 and Echovirus. Age group involved is 6 mt to 3 yr. Incubation period → 5 to 15 days. Clinical manifestations Abrupt onset with high-grade fever, mild pharyngitis and Coryza. The temperature comes down rapidly in 3 to 4 days when a macular or maculopapular rash appears, starting from the trunk and sometimes extending to the extremities and face. The rash lasts for 24 hours, and disappear in 1-2 days without pigmentation or desquamation. There is occipital and post-auricular lymphadenopathy.