• Exanthem subitum
  • Incubation period of 5–15 d
  • Mode of acquisition unknown:
    • Horizontal spread by oral shedding suggested
    • It is spread person to person but is not very contagious
    • Human is the only host
  • Pathophysiology:
    • Complex immune response (cytokines, antibody responses, T-cell reactivity)


  • Human herpesvirus 6 (HHV-6) is most request cause:
    • Large, double-stranded DNA
    • Closely related to human cytomegalovirus
  • Peak incidence at 6–12 mo; 90% occurrence within first 2 yr
  • Highest incidence in late spring and early summer

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