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Herpes simplex is a viral infection that mainly affects the mouth or genital area.

There are two strains of herpes simplex viruses:

• Herpes simplex virus type 1 (HSV-1) is usually associated with infections of the lips, mouth, and face. It is the most common herpes simplex virus and many people develop it in childhood. HSV-1 often causes sores (lesions) inside the mouth, such as cold sores (fever blisters), or infection of the eye (especially the conjunctiva and cornea). It can also lead to infection of the lining of the brain (meningoencephalitis). It is transmitted by contact with infected saliva. By adulthood, 30 - 90% of people will have antibodies to HSV-1. The likelihood of childhood infection is higher among those with lower socioeconomic status.
• Herpes simplex virus 2 (HSV-2) is usually, but not always, sexually transmitted. Symptoms include genital ulcers or sores. However, some people with HSV-2 have no symptoms. Up to 30% of adults in the U.S. have antibodies against HSV-2. Cross-infection of type 1 and 2 viruses may occur from oral-genital contact. That is, you can get genital herpes on your mouth, and oral herpes on your genital area.

A finger infection, called herpetic whitlow, is another form of HSV infection. It usually affects health care providers who are exposed to saliva during procedures. Sometimes, young children also can get the disease.

HSV can infect a fetus and cause abnormalities. A mother who is infected with HSV may transmit the virus to her newborn during vaginal delivery, especially if the mother has an active infection at the time of delivery. However, 60 - 80% of HSV infections acquired by newborns occur in women who do NOT have symptoms of HSV infection or a history of genital HSV infection.

It's possible for the virus to be transmitted even when there are no symptoms or visible sores. Two-thirds of people with genital HSV infection have recurrences of their symptoms, and one-third have three or more recurrences (outbreaks) per year.

HSV is never eliminated from the body, but stays dormant and can reactivate, causing symptoms.

• Blisters or ulcers -- most often on the mouth, lips and gums, or genitals
• Enlarged lymph nodes in the neck or groin (usually only at the time of the initial infection)
• Fever blisters
• Fever -- especially during the first episode
• Genital lesions -- there may first be a burning or tingling sensation
• Mouth sores

Many times, doctors can tell whether you have an HSV infection simply by looking at the sores. However, certain tests may be ordered to be sure of the diagnosis. These tests include:

• Blood test for antibodies of HSV (serology)
• Direct fluorescent antibody (DFA) test of cells taken from a lesion
• Viral culture of the lesion

Support groups and dating services are available for people with genital herpes.

The oral or genital lesions usually heal on their own in 7 to 10 days. The infection may be more severe and last longer in people who have a condition that weakens the immune system.

Once an infection occurs, the virus spreads to nerve cells and stays in the body for the rest of a person's life. It may come back from time to time and cause symptoms, or flares. Recurrences may be triggered by excess sunlight, fever, stress, acute illness, and medications or conditions that weaken the immune system (such as cancer, HIV/AIDS, or the use of corticosteroids).

• Eczema herpetiform (widespread herpes across the skin)
• Encephalitis
• Infection of the eye -- keratoconjunctivitis
• Infection of the trachea
• Meningitis
• Pneumonia
• Prolonged, severe infection in immunosuppressed individuals

Call your health care provider if you develop symptoms that resemble a herpes infection. There are many different conditions that can cause similar lesions (especially in the genital area).

If you have a history of herpes infection and develop similar lesions, tell your health care provider if they do not get better after 7 to 10 days, or if you have a condition that weakens your immune system.

Preventing HSV infection is difficult because people can spread the virus even when they don't have any symptoms of an active outbreak.

Avoiding direct contact with an open lesion will lower the risk of infection.

People with genital herpes should avoid sexual contact when they have active lesions. Safer sex behaviors, including the use of condoms, may also lower the risk of infection.

People with active HSV lesions should also avoid contact with newborns, children with eczema, or people with suppressed immune systems, because these groups are at higher risk for more severe disease.

To decrease the risk of infecting newborns, a cesarean delivery (C-section) is recommended for pregnant women who have an active HSV infection at the time of delivery.

Whitley RJ. Herpes simplex virus infections. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier. 2007: chap 397.