I.

Introduction

Herpes (Greek herpein, “to creep”), name applied to several types of skin eruptions characterized by formation of blisters. The term embraces primarily two distinct disorders, herpes simplex and herpes zoster, both caused by types of herpes viruses. Other herpes viruses include Epstein-Barr virus, the cause of infectious mononucleosis (see Mononucleosis, Infectious) and cytomegalovirus, which can lead to birth defects when the virus invades pregnant women. Together, these viruses are estimated to cause more human illnesses than any other group of viruses.

II.

Herpes Simplex

Two types of herpes simplex virus (HSV) are known. The first type (HSV-1) causes cold sores or fever blisters—an eruption of blisters that often occurs during the course of or after one of a variety of diseases associated with fever (most commonly colds, influenza, and pneumonia). The blisters usually appear around the mouth and on the lips (herpes labialis); about the nose, face, and ears; and in the mouth and pharynx. The causative virus has been shown to be present in the cell bodies of the facial nerve in people who do not have blisters. It is this reservoir of latent virus that is the source of repeated attacks. Except for lotions to relieve pain, itching, or inflammation, no established therapy has been developed.

The second type of herpes simplex virus (HSV-2) is the usual cause of genital herpes (see Sexually Transmitted Infections). Herpetic infections of the genital area have become increasingly common. Sometimes accompanied by headache and fever, the condition usually begins with a mild itching, followed by the development of clusters of blisters that break and crust to form scabs that eventually dry up. The process may last one to three weeks. In many cases new clusters of blisters appear as others heal. When a baby is born to a woman who has active genital herpes lesions, the infant is at high risk of contracting an often fatal infection, so these infants are often delivered by cesarean section. Primary cases of genital herpes can be treated by acyclovir, a drug approved in ointment form in 1982 and in oral form in 1984. It is also proving useful against recurrent attacks.

The virus can also invade the central nervous system, especially in people who are weakened by other diseases, such as cancer, causing a severe encephalitis. Early treatment of herpetic encephalitis with the drug acyclovir can prevent death and brain damage in many instances. Although herpes simplex is incurable, some cases are preventable. Research published in 2009 indicates that among men who engage in heterosexual intercourse, circumcised men are 25 percent less likely to develop HSV-2 than those who are not circumcised.

III.

Herpes Zoster

Known as shingles, this is a recurrence of the symptoms of chicken pox, usually during adulthood. It is caused by the chicken pox virus attacking a sensory nerve. The skin over the nerve generally breaks out in blisters a few days after the onset of the disorder, which is accompanied by pain and frequent numbness or hypersensitivity along the course of the nerve, usually the trunk. The blisters are at first clear, but become cloudy within a few days and form crusts that dry up after five or ten days.

The skin manifestation of herpes zoster is not serious, but the pain caused by the inflammation of the underlying nerve can be severe, lasting for weeks; recovery may be followed by persistence of neuralgia in the area of the involved nerve. High doses of acyclovir can significantly reduce the symptoms of herpes zoster. Normally, medication relieves pain, and the disease subsides spontaneously. More severe cases may be treated with such steroids as cortisone. In cases of persistent pain, the involved nerve may be either blocked by drugs or cut.

In people with cancer being treated with drugs, herpes zoster infections can be fatal. Japanese scientists have developed a vaccine with which they have inoculated children being treated for leukemia. Their results indicate that the vaccine is safe and that it prevents severe herpes zoster infection in these patients. In 2006 the United States Food and Drug Administration approved the first shingles vaccine for use in adults. The Centers for Disease Control and Prevention recommends that all people aged 60 years and older receive the one-time vaccination.

Herpetic infections of the eye, called dendritic keratitis, can cause scarring of the cornea. They are treatable with idoxuridine and vidarabine.