Fifth disease, also called Erythema infectiosum, is a common childhood skin disorder caused by infection with PV-B19, a member of the Parvoviridae family of viruses. It is characterized by a mild rash.
Fifth disease got its name because it was fifth in a list of historical classifications of common skin rash illnesses in children.
Parvovirus B19 infection is common and occurs world wide. The disease is most common in children aged 6-10 years, but it can occur at any age; adults may suffer flu-like symptoms without the classic skin eruption. Worldwide, epidemics of erythema infectiosum tend to occur in the late winter or early spring, with cyclical peaks of incidence occurring every 4-7 years. Recent epidemic years have been 1989-1990, 1993-1994 and 1997-1998. The virus is transmitted effectively after close contact, and possibly also by respiratory secretions. The incubation period is 13-18 days, but can be as long as 20 days. Once the rash is present, the subject is no longer infectious. Approximately 60% of adults are seropositive for PV-B19 by age 20 years. Infection rates vary from 20-50% in schools and households during outbreaks.