Understanding the Diagnosis: Congenital vs. Neonatal HSV

Learning that your newborn has a herpes simplex virus (HSV) infection is overwhelming. While HSV is a common virus in adults, it requires specialized care when it affects a baby. Understanding how and when the virus was transmitted is a vital first step in your baby’s care journey.

Two Types of One Virus

The herpes simplex virus comes in two main “types,” but both can affect a baby similarly:

• HSV-1: Traditionally associated with cold sores on the mouth, it is now a very common cause of neonatal infections ^[1].
• HSV-2: Usually associated with genital herpes.

In newborns, the specific type (1 or 2) is less important than how the baby was exposed and where the virus is located in their body ^[1][2].

Congenital vs. Neonatal Infection

Doctors distinguish between infections that happen inside the womb and those that happen during or after birth.

Congenital HSV (In Utero)

Congenital HSV is extremely rare, representing only about 5% of all infant HSV cases ^[3][2]. This occurs when the virus crosses the placenta or reaches the baby while they are still developing in the uterus.

• Timing: The infection is present at the moment of birth ^[4].
• Signs: Babies may be born with a specific “triad” of symptoms: skin vesicles (blisters) or scarring, eye issues (like chorioretinitis), and neurological findings such as a small head size (microcephaly) ^[5][6].
• Diagnosis: Because this can happen even if a mother has no history of herpes, doctors may use specialized tests, such as checking the umbilical cord for the virus ^[4][5].

Neonatal HSV (Intrapartum or Postpartum)

The vast majority of cases (95%) are neonatal HSV, meaning the baby was exposed around the time of birth ^[3].

• Intrapartum Transmission (85%): This occurs during labor and delivery if the baby comes into contact with the virus in the birth canal ^[3]. Most mothers of infants with neonatal HSV actually have no known history of genital herpes ^[4].
• Postpartum Transmission (10%): This happens after birth, often through contact with a caregiver who has an active cold sore (HSV-1) or by touching a lesion and then touching the baby ^[3][1]. It is crucial to note that mothers with active herpetic lesions on their breasts must avoid breastfeeding from the affected breast, as this can directly transmit the virus to the infant and cause fatal postnatal infection ^[3].

Clinical Categories of Infection

Regardless of how the baby was exposed, doctors categorize neonatal HSV into three types based on where the virus is active:

1. Skin, Eye, and Mouth (SEM) Disease: The virus is limited to external surfaces. While this has the best prognosis, it requires prompt treatment to prevent the virus from spreading deeper into the body ^[7][8].
2. Central Nervous System (CNS) Disease: The virus has reached the brain. This may cause symptoms like lethargy (extreme tiredness) or seizures ^[9][10].
3. Disseminated Disease: This is a systemic infection where the virus affects multiple organs, such as the liver or lungs. It is the most serious form and often mimics the signs of a severe bacterial infection (sepsis) ^[11][12].

Early Action and Empowerment

If doctors suspect HSV, they will likely start your baby on an antiviral medication called acyclovir immediately, often before all test results are back ^[13][14]. This “safety first” approach is the standard of care to ensure the best possible outcome.

While the NICU environment is stressful, your care team is focused on stopping the virus from replicating. You are an essential part of the team; your observations of your baby’s skin and behavior provide critical information to the doctors and nurses ^[1].