Herpes Simplex

Herpes simplex virus (HSV) is a common virus affecting humans. It is perhaps best known as the cause of cold sores, the facial blisters that sometimes occur following a cold or fever. There are two types of herpes simplex viruses. Type 1 primarily involves the face and eyes and type 2 primarily causes genital infections. Each year in the United States, approximately 25 million people have flare-ups of facial herpes, and 5 million develop genital herpes. There are about 500,000 people in the United States with a history of herpetic eye disease. Transmission is via contact of infected secretions (saliva or genital) with mucous membranes or with open skin. HSV-2 is spread primarily sexually, and its rates are variable among different adult populations, depending on sexual behavior.

After exposure, the virus replicates locally in the epithelial cells, causing lysis of the infected cells and producing an inflammatory response. This response results in the characteristic rash, which consists of small, thin-walled vesicles on an erythematous base. Continued replication results in viremia in immunocompromised hosts but rarely in normal hosts. Following primary infection, the virus becomes latent in a sensory nerve ganglion.

Gingivostomatitis and pharyngitis are the most frequent clinical manifestations of first-episode HSV-1 infection, while recurrent herpes labialis is the most frequent clinical manifestation of reactivation HSV infection. HSV pharyngitis and gingivostomatitis usually result from primary infection and clinical symptoms and signs include fever, malaise, myalgias, inability to eat, irritability, and cervical adenopathy. Recurrent oral lesions occur in 60 to 90 percent of infected individuals, are usually milder, and generally occur on the lower lip at the outer vermilion border. The recurrences often are triggered by local trauma, sunburn, or stress.

First-episode primary genital herpes is characterized by fever, headache, malaise, and myalgias. Pain, itching, dysuria, vaginal and urethral discharge, and tender inguinal lymphadenopathy are the predominant local symptoms. Widely spaced bilateral lesions of the external genitalia are characteristic. Lesions may be present in varying stages, including vesicles, pustules, or painful erythematous ulcers. The clinical courses of acute first-episode genital herpes among patients with HSV-1 and HSV-2 infections are similar. However, the recurrence rates of genital disease differ with the viral subtype: the 12-month recurrence rates among patients with first-episode HSV-2 and HSV-1 infections are 90 percent and 55 percent, respectively.

HSV infection of the eye is the most frequent cause of corneal blindness in the United States. HSV keratitis presents with an acute onset of pain, blurring of vision, chemosis, conjunctivitis, and characteristic dendritic lesions of the cornea. Debridement, topical antiviral treatment, and/or interferon therapy hastens healing. However, recurrences are common, and the deeper structures of the eye may sustain immunopathologic [Page 844]injury. Chorioretinitis, usually a manifestation of disseminated HSV infection, may occur in neonates or in patients with human immunodeficiency virus (HIV) infection. Many aspects of mucocutaneous and visceral HSV infections are amenable to antiviral chemotherapy, such as acyclovir, valacyclovir, and famciclovir.