Delivery associated herpes simplex infection in the neonate occurs one in 2000 to one in 5000 deliveries. Herpes Simplex Virus type (HSV-2) two is usually responsible for the disease because HSV-2 is tropic for the genital region through which infants pass during delivery. HSV-2 is responsible for an estimated 70% of all cases. However, HSV-1 can also be responsible for the disease, especially when the genital region of the mother is infected with HSV-1. Transmission is not limited to intrapartum contact with infected maternal genital secretions but also has been documented as a postnatal event.
In 90% of neonates with HSV, visceral and/or CNS involvement develops. Without therapy, the mortality of neonatal herpes is 65%. Only 10% of infected neonates with CNS involvement will develop normally.