Reasons for the Absence of a History of Recurrent Genital Infections in Mothers of Neonates Infected with Herpes Simplex Virus

Thirty-one cases of neonatal herpes simplex (HSV) infection were evaluated to determine how often mothers of infected infants lacked a history of recurrent genital infections and the reasons for its absence. A history of recurrent genital infections was elicited from eight (26%) of the mothers. Nine (29%) of the mothers had primary infections; three of these were oral and six were genital. The mother was not the source of infection in three (9.6%) cases. In eleven (35%) cases, the mother had antibody to HSV but did not have a history or findings of primary or recurrent infection. Two of these mothers had positive cervical or vaginal cultures, but neither had genital lesions typical of HSV in the perinatal period. Two mothers had recurrent HSV infections documented later. The source of the HSV infection remained uncertain in 23% of cases including two in which only the father had a history of recurrent genital infection. When mothers with primary infections in the perinatal period were excluded, the HSV neutralization titers of the mothers of infected infants were similar to the titers of the mothers with recurrent genital infections whose infants were not infected. In contrast, the infected infants had titers fourfold lower than their mother's titer as well as fourfold lower than the 16 infants exposed to HSV who remained uninfected. This discrepancy suggests that the mothers may have had a rise in titer late in pregnancy or that placental transport of antibody was limited. Although 26% of the mothers of infected infants had recurrent genital infections, only three (9.6%) had an easily elicitable history. Most cases of neonatal HSV infection will not be avoidable until the epidemiology of primary maternal infection and of nonmaternal sources of infection is understood and the identification of women with HSV who are never symptomatic is improved.