Herpes cause

herpes causeHerpes cause

Herpes viruses comprise a large family of DNA containing viruses which affect both animals and human. These viruses tend to persist in the body for the whole life, causing periodic disease recurrences.

The virus

The herpesviruses are divided into three groups:

  • the alphaherpesviruses (HSV-1, HSV-2, and  varicella-zoster [VZV]);
  • the  betaherpesviruses (cytomegalovirus, HHV-6, HHV-7);
  • the  gammaherpesviruses (Epstein-Barr virus, Kaposi sarcoma–associated herpesvirus or HHV-8).

Herpes simplex viruses type 1 and 2 possess an internal core with a linear double-stranded DNA. The capsid of herpes viruses consists of 162 consumers. The virus is wrapped in a lipid envelope with viral glycoproteins on the surface. Its molecular weight is approximately 100×106 units and diameter of approximately 160 nm.

Although HSV-1 is considered to cause herpes labialis, it may affect any organ and in at least 50% of cases manifests with genital lesions.

Characteristics of HSV infection

Specific features of HSV infection include the following:

  • The ability of HSV to replicate and remain in the nervous system;
  • The virus remains in the ganglia – when orofacial lesions appear the virus is found in the trigeminal ganglia, in case of genital herpes – in the sacral nerve root ganglia.
  • The infection tends to reactivate induced by fever, traumas, stress, impaired immunity.

Epidemiology

Although HSV-1 is considered to cause herpes labialis, it may affect any organ and in at least 50% of cases manifests with genital lesions.

By the age of 50 almost 90% of adults are infected with HSV-1. It was estimated that every year in the world occur more than 23 million of new HSV-2 infections.

See also: Herpes zoster infection

Transmission

HSV is acquired through close contact with an infected person, regardless of the fact whether the disease is symptomatic or not.

HSV-1 is transmitted by oral-to-oral contact and exposure to infected saliva, whereas HSV-2 is a sexually transmitted infection. No animal reservoirs are known.

Causes of rash

Herpes simplex virus is able to affect all the organs and membranes of the body. The incubation period may last from 1 up to 26 days (usually 6-8 days).

HSV enters the cells of the skin and mucous membranes and starts to replicate. The entire viral production cycle lasts from 4 to 6 hours, an affected cell survives for 16-20 hours.

The virus causes ballooning of the epithelial cells, the cellular membranes are damaged and the formation of giant cells with multiple nuclei follows. This results in the development of vesicles which contain clear fluid. Around these vesicles erythema occurs due to inflammatory response. As the time passes the fluid in the vesicles become purulent. Scarring occurs rarely.

The ulcers are more common for the mucous membranes because of their epithelium fragility in these regions. However, the lesions of the mucosa are formed via the same processes as the skin lesions.

Herpes I test

Herpes HSV1 test

Virus retention and disease recurrence

Viruses later travel to the ganglia via the nerves where they remain for all individual’s life as the infected nerve cells do not die (infection latency) and the disease recurrence may occur under certain circumstances (reactivation of the virus induced by fever, traumas, immunosuppression, emotional stress etc) – the virus reactivation.