HHV-6 and HHV-7 infections

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

Diagnosis

 * Based on clinical signs;
 * serology – IgG and IgM antibodies by immunofluorescence or ELISA methods;
 * cultivation – demanding, on special lymphocyte soils;
 * PCR – from different tissues, the most sensitive method.

Manifestation of an infection
Primary infection usually happens during childhood, often without symptoms. HHV-6 causes one of the most well-known manifestations of these viruses - a minor febrile condition in infants and young children with either exanthema - exanthema subitum (sixth disease), or without skin manifestations. The severity increases with the occurrence of febrile convulsions. HHV-7 infection also has similar symptoms. The infection spreads through the air. After an incubation period of 5-12 days, the pacient has a high temperature without catarrhal manifestations  that last for about 3 days, which is typical for the disease. At the time of the temperature drop, there is a small rash, which must be distinguished from a toxoallergic rash (which is cased by ATB, that are often administered). Rare clinical manifestations include encefalititis, hepatitis or infectious mononucleosis.

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

HHV-6A is more neurotropic, often detectable in patients with and infectious CNS disease (multiple sclerosis).

Therapy
Therapy is symptomatic.

Literature

 * Human herpesvirus 6
 * Human herpesvirus 6