Merck Manual

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Genital Herpes


Kenneth M. Kaye

, MD, Harvard Medical School

Reviewed/Revised Dec 2023
Topic Resources

Genital herpes is a sexually transmitted infection caused by the herpes simplex virus that causes recurring episodes of small, painful, fluid-filled blisters on and around the genitals.

After the first (primary) infection, HSV, like other herpesviruses, remains inactive (dormant or latent) in the body for life. A latent infection may not cause symptoms again, or it may periodically reactivate and cause symptoms.

The primary HSV infection produces an eruption of tiny blisters. After the eruption of blisters subsides, the virus remains in a dormant state inside the collection of nerve cells (ganglia) near the spinal cord that supply the nerve fibers to the infected area. Periodically, the virus reactivates, begins multiplying again, and travels through the nerve fibers back to the skin—causing eruptions of blisters in the same area of skin as the earlier infection. Sometimes the virus is present on the skin or mucous membranes even when no blisters can be seen.

The virus may reactivate many times.

Symptoms of Genital Herpes

The first genital HSV infection (genital herpes) can be severe and prolonged, with many painful blisters in the genital and/or anal area. In women, internal blisters may develop in the vagina or on the cervix. Internal blisters are less painful and are not visible. The blisters develop 4 to 7 days after people are infected. Blisters caused by a first genital infection are usually more painful, last longer, and are more widespread than those caused by a recurrent infection.

Fever and a general feeling of illness (malaise) are common, and some people have burning during urination, difficulty urinating, or constipation. Some people have no symptoms.

Recurrences of genital herpes often begin with symptoms (including tingling, discomfort, itching, or aching in the groin) that precede the blisters by several hours to 2 to 3 days. Painful blisters surrounded by a reddish rim appear on the skin or mucous membranes of the genitals. The blisters quickly break open, leaving sores. Blisters may also appear on the thighs or buttocks or around the anus. In women, blisters may develop on the vulva (the area around the opening of the vagina). These blisters are usually obvious and very painful. A typical episode of recurring genital herpes lasts a week.

Bacteria sometimes infect genital sores due to HSV infection. Such sores may appear more irritated or have a thick or foul-smelling discharge.

Images of Genital Herpes

Diagnosis of Genital Herpes

  • Testing of a sample taken from the sore

Herpes simplex virus infection is usually easy for doctors to recognize. If unsure, doctors may use a swab to take a sample of material from the sore and send the swab to a laboratory to grow (culture) and identify the virus.

Material from the sore can also be tested using polymerase chain reaction (PCR) to identify the herpes simplex DNA. PCR is a more sensitive test than viral culture, which means that PCR will miss fewer cases of the virus.

Sometimes doctors examine material scraped from the blisters under a microscope. Although the virus itself cannot be seen, scrapings sometimes contain enlarged infected cells (giant cells) that are characteristic of infection by a herpes-type virus.

Blood tests to identify antibodies to herpes simplex virus can also be helpful. (Antibodies Antibodies One of the body's lines of defense ( immune system) involves white blood cells (leukocytes) that travel through the bloodstream and into tissues, searching for and attacking microorganisms and... read more Antibodies are produced by the immune system to help defend the body against a particular attacker, such as herpes simplex virus.)

Certain blood tests can distinguish between HSV-1 infection and HSV-2 infection.

Treatment of Genital Herpes

Antiviral medications

Primary genital herpes simplex infections are treated with an antiviral medication such as acyclovir, valacyclovir, or famciclovir (see table Some Antiviral Medications for Herpesvirus Infections Some Antiviral Drugs for Herpesvirus Infections Some Antiviral Drugs for Herpesvirus Infections ). All three antivirals can help improve symptoms and shorten the duration of the illness. No current antiviral medications can get rid of HSV infection, and treatment of a first genital infection does not prevent the dormant infection of nerve cells.

Recurrent infections can be treated with antivirals, such as acyclovir, valacyclovir, or famciclovir, which may relieve discomfort slightly and help symptoms resolve a day or two sooner (see table Some Antiviral Medications for Herpesvirus Infections Some Antiviral Drugs for Herpesvirus Infections Some Antiviral Drugs for Herpesvirus Infections ). Treatment is most effective if started early, usually within a few hours after symptoms start—preferably at the first sign of tingling or discomfort, before blisters appear. For people who have frequent, painful attacks, the number of outbreaks can be reduced by taking antivirals every day indefinitely (this is called suppressive therapy). However, taking antiviral medications does not prevent infected people from transmitting the infection. These antivirals are available by prescription only.

Severe HSV infections, such as can occur in immune suppressed individuals, are treated with acyclovir given intravenously.

Other treatments

For people who have minimal discomfort, the only treatment needed for recurring genital herpes is to keep the infected area clean by gentle washing with soap and water.

Pain relievers may be taken for pain.

Prevention of Genital Herpes

Because HSV infection is contagious, people with genital herpes should use condoms Condoms Barrier contraceptives physically block the sperm’s access to a woman’s uterus. They include condoms, diaphragms, cervical caps, contraceptive gels, contraceptive sponges, and spermicides (foams... read more Condoms at all times. Even when there are no visible blisters and no symptoms, the virus may be present on the genitals and can be spread to sex partners. Because condoms protect only the penis and areas touched by the penis, other areas on the genitals are still at risk even when condoms are used. For example, a herpes sore on a woman's labia may cause infection of skin near the penis.

Pregnant women should tell their doctor if they have had a past genital herpes infection or have a new infection during pregnancy. Women who have an outbreak of genital herpes at any time during pregnancy should be treated with antivirals starting at 36 weeks of pregnancy to decrease the risk of an outbreak at the time of delivery. If women have a genital herpes outbreak at the time of delivery, a cesarean delivery Cesarean Delivery Cesarean delivery is surgical delivery of a baby by incision through a woman’s abdomen and uterus. In the United States, up to 30% of deliveries are cesarean. Doctors use a cesarean delivery... read more Cesarean Delivery is done to prevent transmission to the newborn.

Drugs Mentioned In This Article

Generic Name Select Brand Names
Sitavig, Zovirax, Zovirax Cream, Zovirax Ointment, Zovirax Powder, Zovirax Suspension
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