General Characteristics and Epidemiology
Basic features of HHV-6 and HHV-7
- Family: Herpesviridae
- Subfamily: Betaherpesvirinae
- Genus: Roseolovirus
- Human betaherpesvirus 6A
- Human betaherpesvirus 6B
- Human betaherpesvirus 7
- DNA viruses:
- Double stranded
- DNA core
- Icosahedral capsid
- Lipid envelope with glycoprotein spikes
The clinical relevance of HHV-6A is not entirely known.
- HHV-6B and HHV-7 are associated with:
- Roseola infantum (also known as exanthem subitum, roseola, or 6th disease)
- Acute febrile respiratory disease
- Febrile seizures
- Reactivation syndromes in transplant recipients:
- Pityriasis rosea
- Lichen planus (HHV-7)
- > 70% of adults are seropositive.
- Infection generally occurs by the age of 2 years.
- > 95% of adults are seropositive.
- Infection often occurs in childhood.
Humans are the reservoir for HHV-6 and HHV-7.
HHV-6 and HHV-7 are transmitted through contact with saliva.
- Replication occurs in T lymphocytes.
- Viral entry through:
- HHV-6: CD46 receptor
- HHV-7: CD4 receptor
- Viral DNA is released into the nucleoplasm → production of viral proteins and replication
- Lytic replication → cell death
- Low-level persistent infection occurs in the salivary glands.
- HHV-6: occurs in monocytes
- HHV-7: occurs in T lymphocytes
Human herpesvirus-6 infections are usually mild and occur during childhood. Most HHV-7 infections are asymptomatic.
- High fever:
- Lasts approximately 3–5 days
- Resolves abruptly
- Follows resolution of fever
- Lasts approximately 1–2 days
- Maculopapular or macular
- Rose-pink or red color
- Starts on neck and trunk
- Spreads to face and extremities
- Other manifestations:
- Edematous eyelids
- Otitis media
- Nagayama spots (erythematous uvulopalatoglossal papules)
- Bulting fontanelle
Diagnosis and Management
The diagnosis is clinical, and testing is rarely indicated. An exception is made in the case of severe disease in immunocompromised individuals (e.g., encephalitis, myocarditis).
- PCR to detect viral DNA
- Indirect immunofluorescence
Treatment is generally not necessary, as symptoms are self-limiting. Patients with severe disease may be given:
- Note: Data for these treatments are limited.
Comparison of Herpesviruses
The following table compares the 9 herpesviruses considered endemic in humans; there are 115 different total known species of herpesviruses, grouped into 3 families:
- Alpha (infect epithelial cells and produce latent infection in post-mitotic neurons)
- Beta (infect and produce latent infection in a variety of cell types)
- Gamma (produce latent infection, mainly in lymphoid cells)
|HHV||Common name||Primary target cells||Latency site||Clinical presentation*|
|HSV-1||Mucoepithelial cells||Dorsal root ganglia|
|EBV||Memory B cells|
|CMV||Hematopoietic progenitor cells in bone marrow|
| 6A, 6B|
|Kaposi sarcoma–associated herpesvirus||B cells||Kaposi sarcoma|
EBV: Epstein-Barr virus
HHV: Human herpesvirus
HSV: herpes simplex virus
KSHV: Kaposi sarcoma-associated herpesvirus
VZV: varicella-zoster virus
Comparison of Common Childhood Rashes
|Number||Other names for the disease||Etiology||Description|
|1st disease||Measles morbillivirus|
|2nd disease||Streptococcus pyogenes|
|3rd disease||Rubella virus|
|4th disease||Due to Staphylococcus aureus strains that make epidermolytic (exfoliative) toxin|
|5th disease||Erythema infectiosum||Erythrovirus or parvovirus B19 (Primate erythroparvovirus 1)|
|6th disease||Human herpesvirus 6B or 7|
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