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Herpes Overview

Herpes simplex virus (HSV) infections occur worldwide and can only be transmitted between humans. There are two subtypes of HSV: HSV-1 and HSV-2. HSV-1 is commonly associated with oral infection (herpes labialis or cold sores), whereas HSV-2 is associated with genital infection (herpes genitalium or genital herpes). Although HSV-1 and HSV-2 are usually transmitted by different routes and involve different areas of the body, there is an overlap in their distribution, characteristics, and clinical manifestations. For example, 5%-15% of oral infections are caused by HSV-2, whereas 5%-15% of genital infections are caused by HSV-1.

Primary infection refers to the first time an individual is infected with any type of HSV. This primary event may or may not be accompanied by clinical symptoms and the individual may be unaware of the infection. The primary infection can be accompanied by blisters, ulcers, or red inflamed areas (lesions), which may occur at a variety of body sites including the eye and the internal and external areas of the mouth or genitals.

Once HSV has infected an individual it will remain in the body for life, hidden in a dormant state inside nerve cells. In the majority of infected people, the virus remains dormant for life, whereas in approximately a quarter to a thirdof infected individuals, the virus wakes up (reactivates) and replicates In the presence of an intact immune system, such reactivation may be asymptomatic (without symptoms) or it may exhibit with an eruption of blisters around the mouth or in the genital region including the buttocks. Blisters are typically grouped in a 1 cm diameter circle with some redness, crusting, and occasionally ulceration. Individuals who reactivate the virus without obvious clinical symptoms still make copies (excrete) of it in the oral or genital tract. This phenomenon is called viral shedding and viral shedders are at risk of unknowingly spreading the virus to partners through the sharing of utensils, kissing, or sexual intercourse.

Thus, just because you do not suffer from cold sores or genital herpes does not mean that you have not been infected by HSV. Only a laboratory test, looking for HSV-1 and HSV-2 antibodies, can reliably confirm or exclude infection.

When a primary infection with HSV-1 or HSV-2 has occurred, our immune system will create specific antibodies against the viruses. This event is called seroconversion and an individual with detectable antibodies in serum is called seropositive. HSV-1 infection usually occurs earlier in life than HSV-2 and an infection with HSV-2 in an HSV-1 seropositive person or vice versa is called an initial infection as opposed to a primary infection. Individuals who are infected with both viruses will have detectable antibodies to both HSV-1 and HSV-2. Since the viruses are closely related, HSV-1 antibodies partly protect against HSV-2 infection. Thus, an HSV-2 initial infection in a HSV-1 seropositive individual may be milder than a primary HSV-2 infection.

Social and economic status (socioeconomic) and age influence the frequency of HSV-1 infection. In developing countries, seroconversion occurs early in life. In lower socioeconomic populations, approximately 1/3 of children have been infected by 5 years of age; this frequency increases to 70%-80% by early adolescence. In developed countries, approximately 20% of children are infected prior to the age of five. By the second and third decades of life, 40%-60% are infected. Infections with HSV-2 are usually acquired through sexual contact and, therefore, antibodies to this virus are rarely found before the onset of sexual activity.


Asymptomatic infection

No apparent symptoms of infection


Nerve cell extension


These are the singular and plural for a collection of nerve cell bodies (a nerve center) just like a node in an electricity grid


Infected person


Someone with normal immunity


Someone with a decreased level of immunity

Initial infection

When an individual previously infected with HSV-1 becomes infected with HSV-2, or vice versa

Latent virus

Dormant virus


Nerve cell

Primary infection

First contact with HSV-1 or HSV-2


Activation of dormant virus

Recurrent infection

Reactivation of HSV, with or without symptoms


Previously HSV antibody-negative patient becomes HSV antibody-positive

Subclinical infection

Asymptomatic infection

Viral shedding

Virus is present on the skin, genitals, or in the mouth, without clinical symptoms

What diseases are caused by HSV?

Herpes lesions can present on many parts of the body other than the mouth and genitalia, including the eye, fingers (herpetic whitlow), and torso or arms in athletes such as wrestlers (herpes gladiatorum). Eczema herpeticum is a particularly severe form of skin herpes in patients with eczema. Herpes can also infect the central nervous system and may cause disease in pregnant women and their newborns (neonatal herpes). Children who had neonatal herpes may experience frequent skin recurrences at many body sites during childhood. People who have a decrease in their immunity (immunocompromised), such as those infected with human immunodeficiency virus (HIV) or who receive chemotherapy or immunosuppressive drugs after transplantation, are particularly susceptible to herpes disease. These individuals may have chronic herpes lesions or more wide-spread disease as a result of virus reactivation.

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