What causes roseola infantum?

Updated: Oct 09, 2020
  • Author: Christopher R Gorman, MD; Chief Editor: William D James, MD  more...
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The causative agent of roseola infantum was discovered in 1986. The Roseolovirus genus of the beta herpes virus hominis subfamily contains human herpesvirus (HHV)–6 and HHV-7. HHV-6 has 2 variants: HHV-6A and HHV-6B. Their major differences are cellular tropism. Debate has existed whether they represent 2 species.

HHV-6A infection is rarely associated with roseola infantum. HHV-6A is associated with infection in adults who are immunocompromised. HHV-6A infection occurs later in life, and details are lacking.

HHV-6B is the cause of roseola in infants. Because seropositivity is nearly 100% in older children, most primary infections with HHV-6B are asymptomatic. HHV-7 has been identified in a few cases of roseola infantum.

Recurrences of roseola infantum are not common. A well-documented case of a 13-month-old child who had a second episode of roseola exists. In the acute phase of the second episode, HHV-7 was identified and excreted in the saliva. This was followed by excretion of HHV-6.

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