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Epidemiology of herpes simplex virus type 1 infection

Robyn S Klein, MD, PhD
Section Editor
Martin S Hirsch, MD
Deputy Editor
Jennifer Mitty, MD, MPH


Herpes simplex virus type 1 (HSV-1) infections are frequently asymptomatic but can produce a variety of signs and symptoms. These include oral or perioral lesions, ocular infections, nongenital skin lesions, genital skin or mucous membrane lesions, and serious systemic illnesses such as encephalitis and neonatal disease. (See "Clinical manifestations and diagnosis of herpes simplex virus type 1 infection".)

HSV-1 is transmitted from person-to-person via infected oral secretions during close contact. Infection occurs worldwide, equally between the sexes, and without seasonal variation. In the United States, there are estimated to be approximately 500,000 primary infections per annum [1]. The incubation period of oral infections ranges from 1 to 26 days (median 6 to 8 days) and lesions range from 1 to 8 days in duration [2,3]. While infection is lifelong, it is rarely fatal in the immunocompetent host, producing either asymptomatic or mild clinical disease.

Herpetic keratitis continues to be the leading cause of blindness in industrialized countries, with the predominant disease being of the stromal type [4]. Over the past 20 years, the prevalence of the disease has decreased in most developed countries. (See "Herpes simplex keratitis".)


Contact with herpetic lesions or oral secretions can produce infection with HSV-1 [2]. The viral titer is 100 to 1000 times greater when lesions are present [3]; as a result, transmission is much more likely when the patient is symptomatic [2]. Following primary infection, HSV can also sometimes be recovered from the stool [5].

In various series, HSV was obtained from 81 to 88 percent of vesicles, 34 percent of ulcers or crusts, and from the saliva in 3.6 to 25 percent of patients with a positive history or serology [2,6,7].

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Literature review current through: Nov 2017. | This topic last updated: Aug 21, 2017.
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