Human Herpesviruses 6 and 7 (HHV6 and HHV7)

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Key Points

  • Human herpesviruses 6 (HHV-6) and 7 (HHV-7)
    • Characteristics
      • Members of Herpesvirus family
        • Enveloped DNA virus with double-stranded, linear DNA 
          • Herpesviruses are unique in that they get their envelope by budding from nuclear membrane of host cell
      • HHV-7 shares 90% DNA homology with HHV-6
    • Transmission
      • Saliva
        • From mother to infant
        • Salivary glands may be a latent reservoir
      • Perinatal transmission is also possible
    • Pathogenesis
      • Virus replicates in many cells (macrophages, T-cells, salivary glands, neurons)
        • Induces production of cytokines (TNF, IL-1, IFN-gamma)
      • May cause latent infection (like other herpesviruses)
        • Latent in lymphocytes and monocytes
        • May reactivate in immunocompromised hosts
    • Clinical significance
      • Roseola infantum
        • Also known as exanthem subitum and sixth disease
        • Affects babies (7-13 months old)
        • High fever for 3-5 days
          • Temperatures may exceed 40°C (104°F)
          • Thought to result from viral replication and massive induction of fever-inducing cytokines
        • Followed by macular/maculopapular rash
          • starts on neck/trunk, spreads outwards to face/extremities
    • Diagnosis
      • Diagnosis is clinical; labs are rarely useful
    • Treatment
      • Disease is usually self-limited
        • Supportive care