[New knowledge of Zahorsky exanthema subitum (critical 3-day fever-exanthema, roseola infantum].

A survey is given on the history, characteristic symptoms and recent data of the etiology of exanthem subitum (Zahorsky's disease, sixth disease, roseola infantum). Some cases are presented and modern diagnostic techniques for atypical cases are discussed. The disease is caused by an infection with the human herpesvirus-6 (HHV 6; syn.:, "human B-lymphotropic virus", HBLV). Most babies and small children have an asymptomatic infection usually leading to lifelong immunity. The typical "exanthem subitum" develops only in a minority of the infected and susceptible persons. We suggest that the novel human herpesvirus-6 also has the potential of lifelong persistence in humans and can then be shedd at any age in case of acquired immunodeficiencies. World-wide research in this field is carried out by several working groups and new data will be available in a few years.