Between one in 2,500 and one in 10,000 births are complicated by HSV infection, usually HSV-2. Involvement can be localized or disseminated and results from transmission of the virus to the infant at the time of delivery, either by ascending infection after premature membrane rupture or by passage of the infant through an infected genital tract. The risk of transmission is increased in premature births and with the use of fetal scalp monitor electrodes. About 40 to 50 percent of infants born to mothers with primary infections are at risk for the development of severe disease, whereas fewer than eight percent of those born to women with recurrent herpes are at risk for severe disease. Maternal infection is often asymptomatic at the time of delivery, and asymptomatic shedding may occur in women with no known history of genital herpes.
Infection becomes apparent several days to weeks after delivery.
Newborns often present with vesicles or conjunctivitis, or a syndrome resembling neonatal sepsis may be evident. Neurologic signs such as seizures, cranial nerve palsies, and lethargy often predominate and are accompanied by cerebrospinal fluid pleocytosis. Disseminated infection may involve the liver, lungs, or adrenal glands. If untreated, disseminated or central nervous system infection is fatal in more than 70 percent of patients, whereas localized disease is generally self-limited. The characteristic cytopathic effect of the virus is often detectable within a period of 24 to 48 hours.