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Viral illnesses are among the most common reasons that people come to an emergency department (ED). This chapter reviews some of the more serious viral infections that cause disseminated illness or have a predilection for the central nervous system (CNS). Treatment of primary herpes zoster is discussed in Chapter 83, and mononucleosis is discussed in Chapters 68 and 153. Genital herpes is discussed in Chapter 87. Treatment of the human immunodeficiency virus is covered in Chapter 92, and treatment of cytomegalovirus is discussed in Chapter 99.

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Transmission of herpes simplex virus (HSV) occurs by contact of mucous membranes or open skin with infected fluids (saliva, vesicle fluid, semen and cervical fluid) from persons with ulcerative lesions or from those who are shedding the virus without overt disease. Herpes simplex infections are treatable with antiviral drugs, so early recognition of serious infection is important.

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Clinical Features

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Symptomatic HSV-1 infection most commonly results in orolabial lesions, whereas HSV-2 is most often implicated in genital herpes (see Chapter 87). Primary infections typically produce more extensive lesions involving mucosal and extramucosal sites, and may be accompanied by systemic signs and symptoms. Gingivostomatitis and pharyngitis are typical manifestations of primary HSV-1 infection. The lesions are distributed throughout the mouth and consist of small, thin-walled vesicles on an erythematous base, although they do not always become vesicular. The primary lesions generally last for 1 to 2 weeks. In children younger than 5 years, it may present as a pharyngitis or gingivostomatitis associated with fever and cervical lymphadenopathy. Recurrent HSV-1 infections present as herpes labialis. These lesions occur in 60% to 90% of infected individuals, are usually milder, and generally occur on the lower lip at the outer vermilion border. Less common skin manifestations include herpetic whitlow (finger) and herpes gladiatorum (skin), the latter is commonly seen in wrestlers and other athletes involved in close contact sports.

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HSV-1 is one of the most common viral causes of encephalitis in the United States. It occurs most commonly in patients < 20 years and > 50 years of age. The mortality rate for untreated disease is > 70%. The hallmark of HSV encephalitis is acute onset of fever and neurologic symptoms including focal motor or cranial nerve deficits, ataxia, seizures, and altered mental status or behavioral abnormalities. Herpes infections, including herpes zoster, in immunocompromised hosts can lead to widespread dissemination with multiorgan involvement.

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Diagnosis and Differential

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The diagnosis of HSV infection is largely clinical because confirmatory testing takes days to weeks to be performed and thus is of little use in the ED setting. If testing is desired for mucocutaneous lesions, fluid from an unroofed vesicle can be sent for viral culture. Polymerase chain reaction or direct fluorescent antibody testing may also be performed on swabbed tissue. A Tzanck test is generally not useful.

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Temporal lobe lesions on CT scan or MRI are ...

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