Infections caused by HHV-6 and HHV-7

HHV-6 and HHV-7 belong to the family Herpesviridae. HHV-6 is divided into two subspecies, HHV-6A and HHV-6B. They are enveloped viruses that contain double-stranded DNA. The virion size is 120-150 nm. They replicate in the nucleus and mature in the cytoplasm. They are lymphotropic viruses similar to CMV and persist in the organism for life.

Diagnostics

 * Based on clinical signs;
 * Serology - IgG and IgM antibodies by immunofluorescence or ELISA;
 * cultivation - challenging, on special lymphocyte media;
 * PCR - from different tissues, the most sensitive method.

Signs of infection
Primoinfection usually takes place in childhood, often without symptoms. HHV-6 causes one of the most well-known manifestations of these viruses - a non-serious febrile state in infants and young children with either exanthema subitum (sixth disease) or without skin manifestations. Severity increases with the occurrence of febrile cramps. Similar symptoms are also caused by HHV-7. Infection is airborne. After an incubation period of 5-12 days, a high temperature without catarrhal manifestations lasting about 3 days is typical of the disease. At the time of the temperature drop, a small exanthema develops, which needs to be distinguished from toxoallergic exanthema (after antibiotics, which are often administered).

The more rare clinical manifestations are encephalitis, hepatitis and potentially infectious mononucleosis syndrome.

In immunosuppressed (lymphoproliferative diseases, after transplantation...) there is a possibility of reactivation of infection.

HHV-6A is more neurotrophic and can often be detected in patients with CNS disease (sclerosis multiplex).

Treatment
Treatment is symptomatic.

Použitá literatura

 * Human herpesvirus 6
 * Human herpesvirus 6