(Exanthem Subitum; Pseudorubella)
Most viruses that infect humans can affect both adults and children and are discussed elsewhere in THE MANUAL. Viruses with specific effects on neonates are discussed in Infections in Neonates. This chapter covers viral infections that are typically acquired during childhood (although many may also affect adults).
Roseola infantum is the most well-described illness to result from human herpesvirus-6 (HHV-6); 2 distinct HHV-6 species, A and B, exist with most if not all clinical disease linked to HHV-6B infection. HHV-6B may also cause central nervous system (CNS) disease in immunocompromised patients (eg, hematopoietic stem cell transplant recipients). Roseola infantum occurs most often in the spring and fall. Minor local epidemics have been reported.
The incubation period is about 5 to 15 days. Fever of 39.5 to 40.5° C begins abruptly and persists 3 to 5 days without any localizing symptoms or signs. Despite the high fever, the child is usually alert and active, although febrile seizures may occur. Cervical and posterior auricular lymphadenopathy often develops. Encephalitis or hepatitis occurs rarely.
The fever usually falls rapidly on the 4th day, and when the fall occurs, a macular or maculopapular exanthem usually appears prominently on the chest and abdomen and, to a lesser extent, on the face and extremities; it lasts for a few hours to 2 days and may be unnoticed in mild cases. In 70% of HHV-6 infections, the classic exanthem does not occur.
It may be suspected when a child aged 6 months to 3 years develops typical symptoms and signs. Testing is rarely needed, but diagnosis of roseola infantum can be confirmed by culture or serologic tests.
Molecular assays (eg, quantitative polymerase chain reaction) are available but are more commonly used to detect viral reactivation.