Herpes simplex is a virus that belongs to the family herpesviridae, which includes many DNA viruses that affect animals, including humans. The family includes the following 8 types of viruses:
- Herpes simplex virus type 1 (HSV-1)
- Herpes virus simplex type 2 (HSV-2)
- Varicella zoster virus (VZV)
- Epstein-Barr virus (EBV)
- Cytomegalovirus (CMV)
- Human herpes virus HHV-6
- Human herpes virus HHV-7
- Human herpes virus HHV-8 or Kaposi's sarcoma-associated herpesvirus
Structure
The herpes simplex virus is composed of an outer lipid bilayer wrapped around a protein cage called a capsid which contains a large double-stranded DNA genome. Around 50% of DNA is similar between HSV 1 and HSV 2.
Infection and incubation
The herpes simplex virus can be transmitted on sexual, intimate or skin-to-skin contact with an infected individual. Most transmission occurs during periods of viral reactivation in an infected individual but can also occur during latent periods.
The risk of transmission is increased if a person makes direct contact with a lesion or if they have small cuts or abrasions on the skin area involved in contact. Herpes can also be spread through contact with the saliva of an infected person, through kissing or even sharing drinks.
Once a person is infected, the virus rapidly replicates within the epithelial cells. This causes death of the epithelial cells and the virus then targets the axons or long fibres in nerve cells where it establishes latent infection.
Herpes simplex establishes permanent infection and cannot yet be eliminated from the body. After primary infection, there is a risk of recurrence and symptom outbreak in the future, especially in immunosuppressed individuals such as those with HIV or those who are receiving immunosuppressive therapy.
Symptoms and appearance
Symptoms include skin ulcers or lesions around the genital area in the case of HSV-2 or around the mouth in the case of HSV-1. Oral herpes is the most common form of herpes and genital herpes is the second most common.
Treatment
There is no cure for herpes. The virus persists in an infected person for years. Antiviral medications are used to control the symptoms of the virus and prevent viral replication and spread.
Further Reading
Results from a nested randomized controlled trial for BCG vaccination against recurrent herpes labialis