Genital herpes simplex virus infection and incidence of neonatal disease in Sweden.

Herpes virus may cause serious infection in a neonate. Although antiviral therapy may improve the outcome, serious sequelae still occur in many survivors and prevention is a challenge. In the majority of cases the mother is the source of infection. Among 48 Swedish children with neonatal herpes 12 had type 1 and 35 type 2 infection. Maternal infection was symptomatic and recognized in 5/12 of the type 1 infections and only in 4/36 type 2 infections. In the Stockholm area genital herpes virus strains from pregnant women are predominantly type 2 (97% of 622 strains). The seroprevalence of herpes type 2 among pregnant women have been rising from 17.1% in 1969 to 31.8% in 1983. In the last ten years approximately 200,000 children have been borne. By extrapolation from the incidence data the number of mothers with overt or latent herpes type 2 infection is estimated to be in the range of 60,000. During this period ten children with neonatal herpes type 2 have been diagnosed: two infected from a mother with primary type 2 infection, in three cases the mother had previous type 1 infection and first time type 2 and in five cases the mother had secondary type 2 infection. In an ongoing sero-surveillance study in the Stockholm area of herpes type 2 antibody activity in mentally retarded children no additional cases of herpes type 2 have yet been identified. Thus the prospective risk of a woman with secondary type genital herpes virus infection to transmit the infection to her baby at the time of delivery is small. The silent nature of the majority of maternal infections makes prevention difficult.