Roseola

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Basics

Omnipresent infection occurring in infancy and childhood. Majority of cases are caused by human herpesvirus 6 (HHV-6); may be associated with other diseases including encephalitis

Description

Acute infection of infants or very young children (1)
Causes a high fever followed by a skin eruption as the fever resolves (1)
Transmission via contact with salivary secretions or respiratory droplet (1)
Incubation period of 9 to 10 days (1)
System(s) affected: skin/exocrine, metabolic, gastrointestinal, respiratory, neurologic
Synonym(s): roseola infantum, exanthem subitum; pseudorubella; sixth disease; 3-day fever (1)

Pediatric Considerations
A disease of infants and very young children (2)

Epidemiology

Predominant age
- HHV-6
  - Infants and very young children (<2 years old) (3)
  - Peak age infection 6 to 9 months, rarely congenital or perinatal infection (1)
  - 95% of children have been infected with HHV-6 by 2 years of life.
- HHV-7
  - Later childhood
  - Mean age of infection 26 months
  - >90% population with HHV-7 by 10 years (1)
Predominant sex: male = female (1)
No seasonal variance

Incidence
Common—accounts for 20% ED visits for febrile illness among children 6 to 8 months (4)

Prevalence

Peak prevalence is between 9 and 21 months (3).
Nearly 100% population carrying HHV-6 by 3 years (1)
Approximately 20% patients with primary HHV-6 have roseola (4).

Etiology and Pathophysiology

HHV-6 and HHV-7 (2)
Majority of cases (60–74%) due to HHV-6
- HHV-6B > HHV-6A (2)
- HHV-6A seen in children in Africa
- HHV-6 binds to CD46 receptors on all nucleated cells (2).
Primary infection typically through respiratory droplets or saliva
Congenital infection/vertical transmission occurs in 1% of cases (1).
- Transplacental transmission
- Chromosomal integration (clinical significance unknown)
Lifelong latent or persistent asymptomatic infection occurs after primary infection (1).
- 80–90% of population intermittently sheds HHV-6/HHV-7 in saliva (2).
- Patients are viremic from 2 days prior to fever until defervescence and onset of rash.
- HHV-6 latency is also implicated in CSF (4).

Genetics
HHV-6 is integrated into the chromosomes of 0.2–3.0% of the population. This leads to vertical transmission of the virus. Clinical significance of this is unknown (1).

Risk Factors

Female gender (3)
Having older siblings (3)
At-risk adults: immunocompromised (5)
- Renal, liver, other solid organ, and bone marrow transplant (BMT) (3)
- HHV-6 reactivation can occur in 1st week posttransplant (5). HHV-6 viremia occurs in 30–45% of BMT within the first several weeks after transplantation (4).
  - Usually asymptomatic (4)
  - Up to 82% of HHV-6 reactivation/reinfection in solid organ transplant (5)
Nonrisk factors (3)
- Child care attendance
- Method of delivery
- Breastfeeding (HHV does not appear to pass through breast milk.)
- Maternal age
- Season

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