Herpes Simplex Virus Infections

Herpes simplex viruses can cause several illnesses, the two most common being oral herpes, which cause lesions * on the face, usually at the lip line, and the closely related genital herpes, which cause lesions in the genital region.

There are two types of herpes simplex virus (HSV): herpes simplex virus 1 (HSV-1) and herpes simplex virus 2 (HSV-2). They are members of the herpesvirus family. Genital herpes is a sexually transmitted disease * (STD). When an HSV infection causes blisters or sores, it is referred to as a herpes outbreak.

Oral herpes causes small, clear blisters on the skin. These are often called cold sores, fever blisters, or sun blisters. Small blisters may combine to form a larger sore. Although they usually occur on the face, especially around the mouth and nose, they can occur anywhere on the skin or mucous membranes * , either singly or in groups. Small HSV sores known as herpetic whitlow can appear on the fingers, especially in children who bite their nails or suck their fingers, thereby spreading the virus from their mouth to their hands. HSV skin infections can occur in other locations where the virus comes in contact with broken skin. The blisters may be painful, and they can break, bleed, and crust over, leaving red spots of healing skin.

Although HSV-1 often causes genital herpes, it is more often the case that HSV-2 is responsible for the sores on the penis in males and on the vulva * , vagina * , and cervix * in females. In genital herpes, both sexes can develop herpes blisters around the anus * and on the buttocks. HSV-2 occasionally produces sores on other parts of the body, such as the mouth or throat. Having genital herpes increases the risk of contracting HIV * from unprotected sex with an HIV-positive individual. Infection with both genital herpes and HIV can also increase the likelihood that HIV will be transmitted to a sexual partner.

Fifty to eighty percent of Americans are infected with HSV-1 by 30 years of age. In addition, at least 45 million Americans—about one in five adolescents and adults—are infected with HSV-2. About twice as many women as men have genital herpes (about one in four women compared with about one in eight men). This rate difference may be because, in cases of sexually transmitted herpes simplex illness, male-to-female transmission of HSV is more likely than female-to-male transmission. Over the decade ending in 2008, the percentage of Americans with HSV-2 infections decreased.

HSV-1 and HSV-2 are both contagious * infections, which are spread very often through direct contact with infected skin or saliva. Children often contract HSV-1 through contact with an infected family member. Kissing or sharing dishes or eating utensils can spread HSV-1 infection.

High school and college wrestlers sometimes develop a condition called herpes gladiatorum, caused by HSV-1, in which herpes blisters develop on the shoulders and back from contact with other wrestlers and with virus-contaminated mats. Rugby players also transmit HSV-1 through physical contact, developing blisters that have been nicknamed “scrum pox.”

HSV-2 is most often spread via unprotected vaginal, oral, or anal sex. HSV-2 cannot be contracted from toilet seats or hot tubs. HSV-1 infection of the genitals can be transmitted through oral-genital or genital-genital contact with an infected person.

When a person has herpes simplex illness, active disease or a herpes outbreak is not necessary for the transmission of the herpes virus (either HSV-1 or HSV-2). Research suggests that at least 60 percent of new HSV infections are acquired from individuals with no noticeable blisters or sores. However, genital herpes is most easily spread through genital-genital or oral-genital contact during an active outbreak or in the few days preceding an outbreak.

With HSV infection (either HSV-1 or HSV-2), most individuals have few or no symptoms of infection and often do not realize that they are infected. They may not become aware of symptoms for years after the primary infection.

HSV-infected individuals often experience itching, tingling, or pain in the area where recurrent lesions develop one or two days prior to the outbreak. These warning symptoms—called a prodrome—signal an early phase in the reactivation of the virus.

Symptoms of active HSV-1 or oral herpes infection include blisters or sores on the lips, face, neck, or shoulders. The blisters are often painful and may be accompanied by fever or other flulike symptoms.

Symptoms of active HSV-2 or genital herpes infection can include:

The length and severity of HSV outbreaks vary greatly. The blisters of a primary infection break, leaving tender sores that may take two to four weeks to heal. Subsequent outbreaks are usually shorter. On average, people with genital herpes experience four to five outbreaks of genital herpes illness each year. Oral herpes outbreaks occur less frequently. Although both HSV-1 and HSV-2 remain in the body indefinitely, over time the frequency and severity of outbreaks of both types usually decrease.

Doctors can often diagnose outbreaks of HSV-1 or HSV-2 based on the appearance and location of the sores. Sometimes, however, sores in the genital region can resemble signs of other STDs.

To diagnose HSV infection conclusively, a blister is scraped—preferably on the first day of an outbreak—and cultured * to see if HSV grows. For a quick diagnosis, a preparation from a blister can be examined under a microscope for signs of the virus. In the absence of active blisters, a blood sample can be tested for antibodies * against HSV or for HSV DNA * .

Antiviral medications such as acyclovir can significantly reduce the frequency, severity, duration, and pain of genital herpes outbreaks. Antiviral drugs can also reduce—but not eliminate—the risk of HSV transmission to sexual partners. Under some circumstances, antiviral medications are administered intravenously * :

Although HSV infections usually are not dangerous, outbreaks of either oral or genital herpes can cause pain, embarrassment, and emotional stress. However, in people with weakened immune systems (such as those with cancer or AIDS * or those who are on immunosuppressants * because of organ transplants * ), HSV infection can cause serious illness or death:

A woman who has a primary HSV infection during pregnancy lacks antibodies against the virus and so can transmit HSV to her fetus * , possibly resulting in preterm birth and other complications, especially if the infection occurs late in pregnancy. Infants born to women with active genital herpes are at risk for HSV infection, which they contract as they pass through the birth canal during delivery. In addition to facial or genital herpes, the newborn may have widespread HSV infection involving the eyes, lungs, liver, or brain. Although immediate treatment with antiviral medications may prevent or reduce the damage, severe neonatal * herpes is fatal in at least 50 percent of cases and as many as two-thirds of surviving infants have lifelong disabilities, including brain damage and intellectual disability * .

Using sunscreen, especially on areas prone to blisters, may reduce the likelihood of an oral herpes outbreak. People with active cold sores around the mouth should always wash their hands before touching their genitals or buttocks to reduce the risk of spreading HSV-1 to these areas.

The only way to absolutely ensure against genital herpes infection is to practice sexual abstinence. Because genital herpes is contagious even in the absence of active sores and since people often do not know that they are infected, a latex * condom should always be used during sexual activity. However, condoms do not protect all parts of the genital region. People with genital herpes should refrain from sex during active outbreaks.

Pregnant women with genital herpes may be treated with antiviral drugs to prevent an outbreak prior to delivery. A woman with active genital herpes should deliver by cesarean section * to reduce the risk of transmitting HSV to her infant.

See also Chickenpox (Varicella) • Sexually Transmitted Infections (STIs): Overview • Shingles (Herpes Zoster)

* lesions (LEE-zhuns) is a general term referring to a sore or a damaged or irregular area of tissue.

* sexually transmitted disease is an infection that can be passed from person to person by sexual contact.

* mucous membranes are the thin layers of tissue found inside the nose, ears, cervix (SER-viks) and uterus, stomach, colon and rectum; on the vocal cords; and in other parts of the body.

* vulva (VUL-vuh) refers to the organs of the female genitals that are located on the outside of the body.

* vagina (vah-JY-nah) is the canal, or passageway, in a woman that leads from the uterus to the outside of the body.

* cervix (SIR-viks) is the lower, narrow end of the uterus that opens into the vagina.

* anus (A-nus) is the opening at the end of the digestive system, through which waste leaves the body.

* HIV, or human immunodeficiency virus (HYOO-mun ih-myoono-dih-FIH-shen-see), is the virus that causes AIDS (acquired immunodeficiency syndrome).

* menstruation (men-stroo-AYshun) is the discharge of the blood-enriched lining of the uterus. Menstruation normally occurs in females who are physically mature enough to bear children. Most girls have their first period between the ages of 9 and 16. Menstruation ceases during pregnancy and with the onset of menopause. Because it usually occurs at about fourweek intervals, it is often called the monthly period.

* contagious (kon-TAY-jus) means transmittable from one person to another, usually referring to an infection.

* lymph nodes (LIMF) are small, bean-shaped masses of tissue containing immune system cells that fight harmful microorganisms. Lymph nodes may swell during infections.

* cultured (KUL-churd) means subjected to a test in which a sample of fluid or tissue from the body is placed in a dish containing material that supports the growth of certain organisms. Typically, within days the organisms will grow and can be identified.

* antibodies (AN-tih-bah-deez) are protein molecules produced by the body's immune system to help fight specific infections caused by microorganisms, such as bacteria and viruses.

* DNA, or deoxyribonucleic acid (dee-OX-see-ry-bo-nyoo-klay-ik), is the specialized chemical substance that contains the genetic code necessary to build and maintain the structures and functions of living organisms.

* intravenously (in-tra-VEE-nus-lee) means given or injected directly through a vein.

* immune system (im-YOON SIS-tem) is the system of the body composed of specialized cells and the substances they produce that helps protect the body against disease-causing germs.

* immunosuppressants (im-yoono- suh-PRES-ants) are substances that weaken the body's immune system.

* AIDS, or acquired immunodeficiency (ih-myoo-no-dih-FIH-shensee) syndrome is an infection that severely weakens the immune system; it is caused by the human immunodeficiency virus (HIV).

* transplants (TRANS-plantz) are organs or tissues from another body used to replace a poorly functioning organ or tissue.

* cornea (KOR-nee-uh) is the transparent circular layer of cells over the central colored part of the eyeball (the iris) through which light enters the eye.

* liver is a large organ located beneath the ribs on the right side of the body. The liver performs numerous digestive and chemical functions essential for health.

* encephalitis (en-seh-fuh-LYEtis) is an inflammation of the brain, usually caused by a viral infection.

* intellectual disability is a condition in which people have below average intelligence that limits their ability to function normally.

* neonatal (nee-o-NAY-tal) means pertaining to the first four weeks after birth.

* fetus (FEE-tus) is the term for an unborn human after it is an embryo, from nine weeks after fertilization until childbirth.

* latex (LAY-tex) is a substance made from a rubber tree and is used in such things as medical equipment (especially gloves), toys, and other household products.

* cesarean section (sih-ZAR-ee-an SEK-shun) is the surgical incision of the walls of the abdomen and uterus to deliver offspring in cases where the mother cannot deliver through the vagina.