At least 50 million Americans have genital HSV infection. This recurrent, incurable disease remains undiagnosed in most infected persons; they often have mild or asymptomatic infections and shed virus intermittently in the genital tract. Although systemic antiviral drugs can partially control the signs and symptoms of herpes, they do not eradicate latent virus and have no effect on recurrence after therapy is discontinued.
Diagnosis. The clinical diagnosis of genital herpes is both insensitive and nonspecific. Many infected persons do not have the typical painful multiple vesicular or ulcerative lesions (Figure 1). Thus, laboratory testing is necessary to confirm the diagnosis and to determine the HSV serotype. Two HSV serotypes have been identified: HSV-1 and HSV-2. Although HSV-1 causes up to 30% of the first episodes of genital herpes, recurrences are much less common with HSV-1 infection than with HSV-2 infection.
Virologic tests. Isolation of HSV in cell culture is the preferred virologic test in patients who have genital ulcers or other mucocutaneous lesions. The sensitivity of culture declines rapidly as lesions begin to heal, usually within a few days of onset. Polymerase chain reaction assay for HSV DNA is the test of choice for detecting HSV in the spinal fluid of patients with suspected CNS involvement.
Type-specific serologic tests. Because false-negative HSV cultures are common, especially in patients with recurrent infection or healing lesions, these tests are useful in confirming a clinical diagnosis of genital herpes. They can also be used to diagnose asymptomatic infection and to test sex partners of infected patients. Routine screening for HSV infection in the general population, however, is not recommended.
Both type-specific and nonspecific antibodies to HSV develop during the first several weeks following infection and persist indefinitely. Accurate type-specific assays for HSV antibodies must be based on the HSV-specific glycoprotein G2 for the diagnosis of HSV-2 infection and glycoprotein G1 for HSV-1 infection. These assays became available in 1999; older assays do not accurately distinguish HSV-1 from HSV-2 antibody. Specifically request a type-specific gG-based assay when ordering serologic testing.
The sensitivities of these tests for detection of HSV-2 antibody vary from 80% to 98%, and false-negative results may occur, especially in the early stages of infection. The specificities of these assays are at least 96%. False-positives can occur, especially in patients with a low likelihood of HSV infection, and a second test may be required.
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