Herpes simplex diagnosis

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Overview
Primary orofacial herpes is readily identified by clinical examination in persons without a previous history of lesions, and with reported contact with an individual with known HSV-1 infection. The appearance and distribution of sores, in these individuals, typically presents as multiple, round, and superficial oral ulcers, accompanied by acute gingivitis. Adults with non-typical presentation are more difficult to diagnose. However, prodromal symptoms that occur before the appearance of herpetic lesions helps to differentiate HSV symptoms from the similar symptoms of, for example, allergic stomatitis. Occasionally, when lesions do not appear inside the mouth, primary orofacial herpes is mistaken for a bacterial infection known as impetigo. Common mouth ulcers (aphthous ulcer), also resemble intraoral herpes, but do not present a vesicular stage.

Genital herpes can be more difficult to diagnose than oral herpes since most HSV-2-infected persons have no classical signs and symptoms. To confuse diagnosis, several other conditions resemble genital herpes, including lichen planus, atopic dermatitis, or urethritis. Laboratory testing is, therefore, often used to confirm genital herpes. Laboratory tests include culture of the virus, direct fluorescent antibody (DFA) studies to detect virus, skin biopsy, polymerase chain reaction (PCR) to test for presence of viral DNA. A Tzanck test (or smear), can also be performed although this cannot differentiate between herpes simplex or varicella (chicken pox) (the primary infection of varicella zoster virus (VZV or shingles). Although these procedures produce highly sensitive and specific diagnoses, their high costs and time constraints discourage their regular use in clinical practice. Serological tests for antibodies to HSV are rarely useful to diagnosis but are important in epidemiological studies. Serologic assays cannot differentiate between antibodies generated in response to a genital versus an oral HSV infection and as such cannot confirm the site of infection. Absence of antibody to HSV-2 does not exclude gential infection because of the increasing incidence of genital infections caused by HSV-1. For these reasons and the diagnostic delay; serology is not routinely used in clinical practice