Infection caused by human herpes virus type 7: causes, symptoms, diagnosis, treatment

Human herpes virus type 7 (HHV-7) is a member of the Roseolovirus genus, Betaherpesvirtis subfamily . Electron microscopic examination revealed typical herpesvirus virions up to 170 nm in diameter. The virion contains an electron-dense cylindrical core, capsid, tegument, and outer membrane and has significant morphological similarity to HHV-6.

Hybridization analysis showed that HHV-7 DNA differs from HSV, EBV, varicella zoster virus and cytomegalovirus DNA. The degree of homology between HHV-7 DNA and HHV-6 DNA is at the level of 57.5-58.8%. and with cytomegalovirus DNA - at the level of 36%.

[ 1 ], [ 2 ], [ 3 ]

Epidemiology of Human Herpes Virus Type 7 Infection

HHV-7 is widespread among the population. The frequency of HHV-7 isolation in children under 11 months is 0%, 12-23 months - 50%, 24-35 months - 75%, over 36 months - 100%.

The prevalence of the infection and the routes of transmission are unknown. In connection with the data on the isolation of HHV-7 from the saliva of infected persons, as well as the persistence of the virus in T-lymphocytes, the possibility of airborne transmission of the infection is suggested, especially in young children, and transmission of the infection during transfusion of blood and its components.

[ 4 ], [ 5 ], [ 6 ], [ 7 ], [ 8 ]

Pathogenesis of infection caused by human herpes virus type 7

It has been established that the HHV-7 receptor is the CD4 glycoprotein. During HHV-7 infection, CD4 T cells show a selective and progressive decrease in the amount of CD4 glycoprotein, which explains the mutual interference between HHV-7 and HIV-1.

Symptoms of Human Herpes Virus Type 7 Infection

The symptoms of human herpesvirus 7 infection are poorly understood. HHV-7 has been associated with sudden exanthema and recurrent exanthema in older children. Primary infection with clinical manifestations is rarely identified. HHV-7 is associated with lymphoproliferative disorders, chronic fatigue syndrome, and immunodeficiency.

Diagnostic criteria for chronic fatigue syndrome (major and minor) have been formulated.

Major (mandatory) diagnostic criteria for chronic fatigue syndrome include constant fatigue and a decrease in performance by 50% or more in previously healthy people, observed for at least 6 months. The second mandatory criterion is the absence of diseases or other causes that can cause such a condition.

Minor criteria of chronic fatigue syndrome can be combined into several groups. The first group includes symptoms of infection caused by the human herpes virus type 7, reflecting the presence of a chronic infectious process: subfebrile temperature, chronic pharyngitis, enlarged lymph nodes (cervical, occipital, axillary), muscle and joint pain. The second group includes mental and psychological problems: sleep disorders (hypo- or hypersomnia), memory loss, increased irritability, decreased intelligence, inability to concentrate, depression, etc.). The third group combines symptoms of vegetative-endocrine dysfunction: rapid change in body weight, gastrointestinal dysfunction, decreased appetite, arrhythmia, dysuria, rapid physical fatigue followed by prolonged (more than 24 hours) fatigue, etc. The fourth group includes symptoms of allergies and hypersensitivity to drugs, insolation, alcohol and some other factors.

According to the diagnostic criteria of 1994, the diagnosis of "chronic fatigue syndrome" is considered reliable if the patient has two mandatory criteria and four signs from the following eight additional ones (which are also observed for at least 6 months):

• memory or concentration impairment;
• pharyngitis;
• painful cervical lymph nodes;
• muscle pain;
• polyarthralgia;
• an unusual headache that is new to the patient;
• unrefreshing sleep;
• malaise after physical exertion.

The prevalence of chronic fatigue syndrome in different countries and socio-demographic groups is approximately the same. People of any age and gender are susceptible to the disease.

It is assumed that HHV-7 may be the cause of exanthema subitum, but not directly, but indirectly, due to the reactivation of HHV-6 from a latent state. When HHV-7 and HIV interact, a competing effect is manifested for the order of infection of CD lymphocytes.

Diagnosis of infection caused by human herpes virus type 7

Diagnosis of infection caused by human herpes virus type 7 is based on the use of indirect immunofluorescence, electron microscopy, and PCR methods.

[ 9 ], [ 10 ], [ 11 ], [ 12 ], [ 13 ]

Treatment of infection caused by human herpes virus type 7

Treatment of infection caused by human herpes virus type 7 is symptomatic.