Herpes simplex
Description
An in-depth report on the causes, diagnosis, treatment, and prevention of herpes simplex.
Alternative Names
Genital herpes; Fever blisters; Cold sores
Transmission
To infect people, the herpes simplex viruses (both HSV-1 and HSV-2) must access the body through broken skin or a mucous membrane such as inside the mouth or on the genital area. Each virus can be carried in bodily fluids (such saliva, semen, fluid in the female genital tract) or in fluid from herpes sores. The risk for infection is highest with direct contact of blisters or sores during an outbreak.
Once the virus has contact with the mucosal surfaces or skin wounds, it begins to replicate. The virus is then transported within nerve cells to their roots where it remains inactive (
latent
) for some period of time. During latent periods, the virus is not transmissible. However, at some point, it often begins to replicate again without causing symptoms (called
shedding
). During shedding, the virus is again transmissible through bodily fluids and can infect other people. Shedding is an especially insidious stage because there are no sores or symptoms and it possibly accounts for about a third of all HSV-2 infections.
In some cases, infected people can transmit the virus and infect other parts of their own bodies (most often the hands, thighs, or buttocks). This process, known as autoinoculation, is uncommon, since people generally develop antibodies that protect against this occurrence.
Transmission of Oral Herpes
Oral herpes (usually HSV-1) has been detected in both the saliva and blood of patients with active oral infections. It is the most prevalent form of HSV, and infection is most likely to occur during preschool years. Oral herpes is easily spread by direct exposure to saliva or even from droplets in breath. Skin contact with infected areas is sufficient to spread it. Transmission most often occurs through close personal contact, such as kissing. In addition, because HSV-1 can be passed in saliva, people should also avoid sharing toothbrushes or eating utensils with an infected person.
Transmission of Genital Herpes
Genital herpes is most often transmitted through sexual activity, and people with multiple sexual partners are at high risk. HSV, however, can also enter through the anus, skin, and other areas.
People with active symptoms of genital herpes are at very high risk for transmitting the infection. Unfortunately, evidence suggests about one-third of all HSV-2 infections occur during times when the virus is shedding but producing no symptoms. In addition, only about 10 - 25% of people who carry HSV-2 actually know that they have the infection. In other words, most people either have no symptoms or don't recognize them when they appear.
Until recently, genital herpes was mostly caused by HSV-2, but HSV-1 genital infection is increasing, most likely to due to oral sex. Shedding of genital HSV-1 is less common than with HSV-2, so HSV-1 is less likely to be transmitted, although transmission obviously still occurs, as evidenced by the rising prevalence of genital HSV-1. In fact, a person who carries both HSV-1 and HSV-2 poses a greater risk for sexually transmitting HSV-2 than a person who only carries HSV-2. A person who is infected only with HSV-1 has some protection
against
being infected by HSV-2.
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Review Date: 10/1/2006
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Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital
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