Newborn infants can become infected with herpes virus while in the uterus (intrauterine herpes), during passage through the birth canal (birth acquired herpes, the most common method of infection), or in the period immediately following birth (postpartum).

If the mother has an active genital herpes infection at the time of delivery, the infant is more likely to become infected during the birthing process. However, it is possible for a mother with a primary (first-time) herpes infection to transmit the virus to a child during birth. In addition, some people have had herpes infections in the past, but have not been diagnosed or treated.

These people may pass herpes on to their child, despite not knowing that they have it themselves. Herpes type 2 (genital herpes) is the most common cause of herpes infection in newborn babies, but herpes type 1 can also occur.

Intrauterine herpes is very rare. It can cause severe brain damage, eye disease, such as inflammation of the retina (chorioretinitis), and skin lesions.

Birth acquired herpes can produce localized or systemic disease. Infants may develop only a localized skin infection consisting of small fluid-filled blisters (vesicles) that rupture, crust over, and finally heal, often leaving a mild scar behind.

A second type of birth acquired herpes infection leads to encephalitis, an inflammation of the brain that can result in seizures and later neurologic problems. If untreated, it may lead to death.

The third type of infection, disseminated herpes infection, is the most dangerous. In this type, the herpes virus can affect many different internal organs including the liver, lungs, kidneys, and brain. There may or may not be vesicles on the skin. This type of infection is frequently fatal.

Herpes acquired in the period shortly after birth behaves similarly to birth acquired herpes.