Herpes simplex viruses belong to the Herpes family of viruses. There are two types of Herpex simplex virus, Herpes simplex virus Type-1, the cause of most recurrent oral herpes infections (cold sores), and Herpes simplex virus Type-2, the cause of most recurrent genital herpes infections.
Approximately 30% of the adult population suffer from recurrent oral herpes infections, and 20% suffer from recurrent genital herpes infections.
Initial Herpes Simplex Infection
Herpes simplex virus Type-1 (HSV-1) can also cause genital infection and Herpes simplex virus Type-2 (HSV-2) can cause oral infections. However, HSV-1 is more likely to cause recurrent oral infections than HSV-2, and HSV-2 is more likely to cause recurrent genital infection than HSV-1.
The initial lesions for HSV-1 and HSV-2 look the same. Infection begins with an area of redness that progress to a fluid-filled blister (vesicle). The base of the lesion is red, sometimes referred to as dewdrop on a rose petal. Fluid in the blister contains infectious virus. The blisters may progress to pus-containing, encrusted lesions and ulcers.
Herpex simplex viruses destroy the cells they infect: sores can be painful as well as nasty-looking!
Severity of herpes simplex infections depend on:
- Site of virus inoculation
- Age and immune status of the host
- Genetic variation in virus strains
- Genetic variation in infected persons
In addition to damage to infected cells caused by the Herpes simplex, the response of the immune system to the invading virus can cause damage to infected cells and tissues. Immune response is largely responsible for corneal damage that occurs with herpetic keratitis (leading cause of corneal blindness caused by HSV-1).
Herpes simplex virus can cause a variety of infections:
- Gingivostomatitis (lesions usually begin on the lips and spread to the mouth, gums and throat)
- Herpes labialis (oral herpes, cold sores)
- Keratoconjunctivitis (herpes infection of the conjunctiva and cornea of the eye)
- Cutaneous herpes
- Genital herpes (usually transmitted through oral sex or intercourse)
- Encephalitis (sometimes fatal viral infection of the brain usually caused by HSV-1)
- Meningitis (viral infection of the tissues surrounding the brain and spinal cord usually caused by HSV-2)
- Neonatal herpes (often fatal infection caused by HSV-2 contracted from the mother in-vitro or during birth)
Cutaneous herpes infections include the following:
- Cold sores (lesions on the lips and nose)
- Herpetic Whitlow (lesions on the hands or wrists resulting from contact of broken skin with infectious herpes lesions),
- Herpes gladiatorum (lesions on the neck and head area resulting from contact with skin lesions between wrestlers)
- Eczema herpeticum (herpes lesions in areas of eczema)
Herpes simplex viruses can cause severe infections in people with compromised immune systems or underlying chronic infections, and in newborn infants.
Reactivation of Latent HSV Infection
Reactivation of latent HSV infection can occur periodically: a number of factors can contribute to reactivation and recurrent infection. Reactivation occurs when HSV travels from the nerve centre (ganglion) back down the axon to the site of initial infection.
The frequency and severity of infection is affected by both the severity of initial infection and the health of the immune system. The more severe the initial outbreak, the larger the number of cells infected and the larger the number of nerve cells in which virus becomes latent. When reactivation occurs, virus from each of the infected nerve cells return to the skin surface resulting in larger areas of infected cells. A healthy immune system is important to restrict the spread of HSV infection.
Read more about herpes infections:
Herpes Infection and Reactivation
Infections Caused by Herpes Virus
Sources:
Judy Arbique - I graduated from Medical Laboratory Technology training in 1979 and since then obtained advanced recognition in clinical microbiology from ...
