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PCR testing for the diagnosis of herpes simplex virus in patients with encephalitis or meningitis

Angela M Caliendo, MD, PhD
Section Editor
Martin S Hirsch, MD
Deputy Editor
Jennifer Mitty, MD, MPH


Although encephalitis is a rare complication of herpes simplex virus (HSV) infection, HSV is the most common cause of nonepidemic, sporadic, acute focal encephalitis in the United States [1,2]. The estimated frequency of HSV encephalitis (HSE) is between 1:250,000 and 1:500,000 persons per year [1]. The administration of acyclovir reduces the mortality from approximately 70 percent in untreated infection to 19 to 28 percent; however, neurologic impairment is common (44 to 62 percent) in those who survive [3,4]. (See "Herpes simplex virus type 1 encephalitis", section on 'Treatment'.)

Given the severity of the illness and the availability of effective therapy, there is a need for a rapid and accurate diagnostic test for HSV encephalitis (HSE). In adults, the infection is usually caused by HSV type 1 and may be due to primary infection or reactivation of latent infection. (See "Herpes simplex virus type 1 encephalitis".)

Neonatal HSV infection occurs in 1:3500 to 1:5000 deliveries in the United States [2]. It is usually acquired by intrapartum contact with infected maternal genital secretions, and is therefore most often due to HSV type 2. There are three general presentations of the disease: skin, eye, and mouth (45 percent); encephalitis (35 percent); and disseminated disease (20 percent), which is often associated with central nervous system (CNS) involvement. Thus, CNS disease occurs in approximately 50 percent of babies with neonatal HSV infection.


The clinical presentation does not distinguish herpes simplex encephalitis (HSE) from encephalitis caused by other viruses such as St. Louis (flavivirus), Eastern equine (togavirus), and Epstein-Barr virus (EBV), or from Mycobacterium tuberculosis meningitis [5]. (See "Viral encephalitis in adults" and "St. Louis encephalitis".)

Culture of herpes simplex virus (HSV) from the cerebrospinal fluid (CSF) of adults with HSE has a sensitivity of less than 10 percent. Better results are obtained with tests that measure HSV antigens or antibodies in the CSF; these tests are associated with sensitivity and specificity rates of 75 to 85 percent and 60 to 90 percent, respectively [2].

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Literature review current through: Dec 2017. | This topic last updated: Sep 24, 2017.
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