Herpes Simplex Virus (HSV) is a common viral infection found globally, with two main types: HSV-1, often associated with oral cold sores, and HSV-2, the primary cause of genital herpes. Both types are highly contagious and transmit through direct contact with sores or viral shedding, even when no symptoms are visible. Herpes is not hereditary; it is not passed down through a person’s genes or DNA. Parent-to-child transmission relates entirely to infectious acquisition of the virus.
Understanding the Difference: Hereditary vs. Infectious
A clear distinction exists between hereditary and infectious conditions. Hereditary conditions are genetic, resulting from variations or mutations in the DNA passed from parent to child through reproductive cells. These conditions are structurally embedded in the offspring’s genome from conception.
In contrast, infectious diseases, like those caused by Herpes Simplex Virus, are acquired when an external pathogen enters the body. HSV is a virus that infects cells, replicates, and spreads through physical contact, not genetic inheritance. The virus is acquired through exposure to the pathogen, typically via contact with active lesions or viral fluids.
Primary Routes of Transmission to Infants
Herpes transmission from a parent to a baby occurs through three primary non-hereditary routes. The most common and dangerous route is perinatal transmission, which happens during delivery as the infant passes through the birth canal. If the birthing parent has active genital lesions or is shedding the virus in the genital tract, the baby is exposed to the virus.
The risk of transmission is highest (30% to 50%) if the birthing parent acquires a first-time genital HSV infection late in the third trimester. This elevated risk occurs because the parent’s immune system has not had time to develop protective antibodies to pass to the baby. If the parent had genital herpes before pregnancy, the risk is very low (typically less than 1%), because maternal antibodies offer some protection.
Congenital transmission is a rare route, accounting for about 5% of cases, where the virus crosses the placenta to infect the fetus in utero. Postnatal transmission accounts for roughly 10% of cases and occurs after birth, often due to contact with an active lesion on a caregiver. This happens if a person with an oral cold sore (HSV-1) kisses the baby or if a caregiver touches a lesion and then touches the infant.
Neonatal Herpes: Signs, Severity, and Treatment
Neonatal herpes is a serious HSV infection in a newborn, especially because a baby’s immune system is underdeveloped. Symptoms typically appear between the first and fourth week of life, though they can manifest as late as six weeks. Early signs may include a high temperature, irritability, lethargy, or difficulty feeding.
The infection is categorized based on the areas of the body affected. The most recognizable form is skin, eye, and mouth (SEM) disease, characterized by fluid-filled blisters. The most severe forms involve the central nervous system (CNS) or disseminated disease, where the virus spreads to major organs like the brain and lungs. CNS involvement can lead to high mortality and significant neurological disability in survivors.
Treatment must begin immediately upon suspicion and involves high-dose intravenous antiviral medication, specifically acyclovir. For babies with localized SEM disease, 14 days of intravenous treatment is followed by a six-month course of oral acyclovir to prevent recurrence. Infants with CNS or disseminated disease require 21 days of intravenous treatment, followed by the same six-month oral regimen, which improves neurodevelopmental outcomes.
Strategies for Risk Reduction and Prevention
Preventing mother-to-child transmission focuses on minimizing the infant’s exposure to the virus during labor and delivery. For birthing parents with a history of genital herpes, medical guidelines recommend suppressive antiviral therapy starting at or beyond 36 weeks of gestation. This therapy, often using acyclovir or valacyclovir, reduces recurrent outbreaks and decreases the likelihood of asymptomatic viral shedding at birth.
Suppressive therapy significantly lowers the need for a Cesarean delivery, which is otherwise indicated if the birthing parent has active genital lesions or prodromal symptoms when labor begins. Postnatal prevention measures are also crucial, particularly avoiding close contact between the baby and anyone with an active cold sore. Caregivers should practice meticulous hand hygiene and should not kiss the baby near the mouth or eyes if a lesion is present.