• HHV-6 causes exanthem subitum (roseola infantum, a common childhood febrile illness with rash) and 10–20% of febrile seizures without rash in infancy.
    • In older age groups, HHV-6 has been associated with mononucleosis syndromes and—in immunocompromised hosts—with encephalitis, pneumonitis, syncytial giant-cell hepatitis, and disseminated disease.
    • More than 80% of adults are seropositive for HHV-6.
  • HHV-7 is frequently acquired during childhood, and infections typically manifest as fever and seizures. The virus is commonly present in saliva.
  • HHV-8 infection in healthy children can present as fever and rash; in immunocompromised pts, primary infection may present as fever, splenomegaly, pancytopenia, and rapid-onset Kaposi’s sarcoma.
    • HHV-8 is associated with Kaposi’s sarcoma, body cavity–based lymphoma in AIDS pts, and multicentric Castleman’s disease.
    • Unlike other herpesvirus infections, HHV-8 infection is much more common in some geographic areas (e.g., central and southern Africa) than in others (North America, Asia, northern Europe).
    • The virus appears to be sexually spread and may also be transmitted in saliva, by organ transplantation, and through IV drug use.

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