Neonatal Herpes Simplex Virus (HSV) is a rare but serious infection that can be transmitted from a mother to her infant. This is often meant by “maternal herpes.” This condition is caused by the herpes simplex virus, which includes HSV-1 (associated with oral cold sores) and HSV-2 (the usual cause of genital herpes). Neonatal HSV is uncommon, affecting approximately one in every 3,200 to 10,000 live births in the United States annually.
This infection carries significant risks for the newborn, including the potential for long-term neurological damage or death if not treated promptly. The severity of the outcome necessitates a high level of awareness regarding the routes of transmission, symptom recognition, and prophylactic measures. Understanding these factors is important for ensuring the best possible health outcomes for the infant.
Understanding How Neonatal Herpes is Transmitted
Transmission occurs during three periods: during pregnancy (in utero), during delivery (intrapartum), and after birth (postnatal). The majority of neonatal HSV cases (approximately 85%) are acquired during passage through the birth canal. This occurs when the infant comes into direct contact with active herpes lesions or viral shedding in the mother’s genital tract.
The risk of transmission depends heavily on the mother’s infection status at the time of delivery. A mother who acquires a primary, first-time genital herpes infection late in the third trimester faces the highest risk of transmission (as high as 30% to 50%). This elevated risk occurs because the mother’s body has not had time to produce protective antibodies that can cross the placenta. Conversely, if a mother has a recurrent herpes outbreak, the transmission risk is much lower, typically less than 1% to 5%, due to the presence of pre-existing maternal antibodies.
Postnatal transmission accounts for about 10% to 15% of cases. This is typically acquired through contact with a caregiver who has an active HSV lesion, such as a cold sore on the mouth. Caregivers with active lesions should avoid kissing the newborn and practice meticulous hand hygiene. While HSV-2 historically accounted for most cases, HSV-1 is becoming increasingly common in newborns in some regions.
Recognizing Symptoms in Newborns
Recognizing symptoms quickly is important because early treatment significantly improves the infant’s prognosis. Symptoms of neonatal HSV often do not appear immediately at birth but typically begin to manifest between one and four weeks of life. The infection is classified into three main categories based on the body systems affected.
The most common form is disease localized to the skin, eyes, and mouth (SEM), which accounts for about 45% of cases. Symptoms include clusters of small, fluid-filled blisters, or vesicles, on the skin. The other two, more serious classifications are central nervous system (CNS) disease, affecting the brain and spinal cord, and disseminated disease, which involves multiple organs like the liver and lungs.
Symptoms of CNS or disseminated disease are often nonspecific and can mimic other conditions like bacterial sepsis. Parents should be alert for subtle signs such as lethargy, poor feeding, fever, irritability, seizures, or temperature instability. In the absence of the characteristic skin lesions, a high index of suspicion is required for any newborn presenting with a sepsis-like illness in the first month of life.
Prevention and Management During Pregnancy
Management during pregnancy is the most effective way to reduce the risk of neonatal HSV transmission. This focuses on preventing the mother from having an active lesion or viral shedding near the time of delivery. Women with a history of recurrent genital herpes should be offered suppressive antiviral therapy starting at 36 weeks of gestation.
The medication most commonly used for this preventative measure is oral acyclovir, taken daily until delivery. This therapy works by reducing the frequency of recurrent outbreaks and the amount of asymptomatic viral shedding at term. While suppressive therapy does not eliminate the risk entirely, it significantly reduces the likelihood of an active outbreak, which decreases the need for a Cesarean section (C-section).
The mode of delivery is decided based on the presence of lesions at the onset of labor. A C-section is recommended for women who have active genital lesions or prodromal symptoms, such as tingling or pain, at the time of labor. Performing the C-section before the rupture of membranes can significantly reduce the infant’s exposure to the virus in the birth canal. If the mother has a history of genital herpes but no active lesions or symptoms, a vaginal delivery is generally considered safe.
Treatment for Infected Infants
Once a newborn is diagnosed with or suspected of having Neonatal HSV, immediate hospitalization and treatment are required. Treatment must be initiated as soon as the infection is suspected, without waiting for confirmatory test results, because early intervention is linked to better outcomes. The standard protocol involves the prompt administration of high-dose intravenous (IV) acyclovir.
The duration of IV treatment depends on the extent of the disease. For localized skin, eye, and mouth (SEM) disease, the course is typically 14 days. If the infection has spread to the central nervous system (CNS) or is disseminated throughout the body, the treatment duration is extended to a minimum of 21 days. After the initial IV course, infants who survived CNS or disseminated disease often require a six-month course of oral suppressive acyclovir to prevent recurrences and improve neurodevelopmental outcomes. Follow-up monitoring, including neurological and ophthalmological examinations, is essential to detect any potential long-term complications.