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Herpes simplex viruses (HSV-1 and HSV-2) are enveloped, double-stranded DNA viruses. They are part of the herpes group, which also includes cytomegalovirus, Epstein-Barr virus, varicella-zoster virus, and human herpes viruses (HHV-6 and HHV-7). HSV infection is among the most prevalent of all viral infections encountered by humans.


The incidence of neonatal HSV infection is estimated to range from 1 in 2000 to 1 in 3000 live births. As of 2014, seroprevalence of HSV-1 and HSV-2 in pregnant women in the United States was approximately 59.3% and 21.1%, respectively.


HSV enters the human host through inoculation of oral, genital, or conjunctival mucosa or breaks in skin, infects the sensory nerve endings, and then passes via retrograde axonal flow to the dorsal root ganglia, where it remains for the life of the host. Two serologic subtypes can be distinguished by antigenic and serologic tests: HSV-1 (usually affects face and skin above the waist) and HSV-2 (genitalia and skin below the waist). Three quarters of neonatal herpes infections are secondary to HSV-2. HSV-1, however, can be the cause of maternal genital herpes infections in 9% of the cases, and its rate appears to be increasing (eg, HSV-1 is the major serotype causing neonatal disease in Australia). HSV infection of the neonate can be acquired at 1 of 3 times: intrauterine, intrapartum, or postnatal. Most infections (85%) are acquired in the intrapartum period as ascending infections with ruptured membranes (the period of 4–6 hours is considered a critical period for this to occur) or by delivery through an infected cervix or vagina. An additional 10% of infected neonates acquire the virus postnatally (eg, from someone shedding HSV from the mouth who then kisses the infant). The final 5% of neonatal HSV infections occur in utero. In utero infection is acquired transplacentally and occurs only in women with primary HSV infection. It is usually associated with placental infarcts and necrotizing funisitis and may result in miscarriage, congenital anomalies, preterm birth, and/or fetal growth restriction. The incubation period is from 2 to 20 days. Three general patterns of neonatal HSV infection are recognized: disease localized to the skin, eyes, and mouth (SEM); central nervous system (CNS) disease (with or without SEM involvement); and disseminated disease (which also may include signs of the first 2 groups). Maternal infection can be classified as either first-episode or recurrent infections. First-episode infections are further classified as either primary or first-episode nonprimary based on type-specific serologic testing. Primary infections are those in which the mother is experiencing a new infection with either HSV-1 or HSV-2 and has not already been infected with the other virus type. First-episode nonprimary infections are those in which the mother has a new infection with 1 virus type, usually HSV-2, but has antibodies to the other virus type, usually HSV-1. Infants born vaginally to ...

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