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

There are two different 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 most people develop it in childhood. HSV-1 often causes lesions inside the mouth, such as cold sores (fever blisters). It is transmitted by contact with infected saliva. By adulthood, up to 90% of people will have antibodies to HSV-1.
• Herpes simplex virus 2 (HSV-2) is sexually transmitted. Symptoms include genital ulcers or sores. In addition to oral and genital sores, the virus can also lead to complications such as infection of the lining of the brain and the brain itself (meningoencephalitis) or infection of the eye (especially the conjunctiva and cornea). However, some people have HSV-2 but do not show symptoms. Up to 30% of U.S. adults have antibodies against HSV-2. Cross-infection of type 1 and 2 viruses may occur from oral-genital contact.

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

The herpes virus can infect the fetus and cause abnormalities. A mother who is infected with herpes may transmit the virus to her newborn during vaginal delivery, especially if the mother has an active infection at the time of delivery.

It's possible for the virus to be transmitted even when there are no symptoms or visible sores.

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

Many times, doctors can tell whether you have a herpes-simplex infection simply by looking at the lesions. However, certain tests may be ordered to be sure of the diagnosis. These tests include:

• Blood test
• Viral culture of the lesion
• Direct fluorescent antibody (DFA) test

Some cases are mild and may not need treatment.

People who have severe or prolonged cases, immune system problems, or frequent recurrences may need to take antiviral medications such as acyclovir (Zovirax), famciclovir (Famvir), and valacyclovir (Valtrex).

People who have more than 6 recurrences of genital herpes per year may need to continue taking antiviral medications to reduce recurrences.

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).

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

Call your health care provider if you develop symptoms which appear to be 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 herpes simplex is difficult since 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 herpes 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 herpes simplex infection at the time of delivery.

Workowski KA, Berman SM. Sexually Transmitted Diseases Treatment Guidelines, 2006. MMWR Morb Mortal Wkly Rep. August 4, 2006;55(RR-11):1-94.

Stoopler ET. Oral herpetic infections (HSV 1-8). Dent Clin North Am. 2005 Jan;49(1):15-29, vii.

Mandell GL, Bennett JE, Dolin R. Principles and Practice of Infectious Diseases. 5th ed. Philadelphia, Pa: Churchill Livingstone; 2000.