Neonatal herpes simplex virus (HSV) is a rare but serious infection occurring in newborns, typically within the first four weeks of life. It is caused by the same virus responsible for cold sores and genital herpes in adults. Due to the infant’s underdeveloped immune system, the infection can quickly spread from localized areas to the brain and internal organs. Immediate medical attention is necessary if neonatal herpes is suspected, as prompt treatment offers the best chance for a favorable outcome.
Recognizing the Visible Signs of Neonatal Herpes
The most recognizable manifestation of neonatal herpes is the Skin, Eyes, and Mouth (SEM) disease, which is the least severe of the three classifications. This localized form is characterized by the appearance of fluid-filled blisters, known as vesicles, on the infant’s skin or mucous membranes.
The lesions typically appear as clusters of small, clear blisters on a reddened or discolored base, similar to an adult cold sore. They may appear on almost any part of the body, but are often found on the scalp, face, or areas that experienced minor trauma during delivery. Vesicles often develop between nine and eleven days after birth, though they can appear up to six weeks later. Without treatment, this localized infection can progress to involve the central nervous system or become disseminated throughout the body.
In the SEM classification, the virus can also affect the eyes, causing conjunctivitis or inflammation of the cornea, known as keratitis. The infant’s eyes may appear red, swollen, or excessively watery. Sores can also be found inside the mouth, sometimes presenting as ulcers on the tongue or the roof of the mouth. Approximately 30% of infants with severe internal disease may not have these skin lesions when they first become ill.
Understanding the Severity of Internal Infection
The virus can rapidly overwhelm the newborn’s immature immune defenses. The infection is classified into three types, with the most severe forms involving the Central Nervous System (CNS disease) or multiple organs (disseminated disease). These systemic infections are associated with increased mortality and morbidity, even with treatment.
The symptoms indicating a severe, internal infection are often non-visual and can mimic other newborn illnesses, such as bacterial sepsis. Signs of CNS disease, which affects the brain and spinal cord, include irritability, lethargy, poor feeding, and seizures. Infants may also exhibit an unstable body temperature, showing either a high fever or hypothermia.
Disseminated disease involves a widespread infection of major organs, commonly the liver, lungs, and adrenal glands. Symptoms can appear around 10 to 12 days after birth and may include breathing difficulties, a swollen abdomen, or jaundice. Regardless of whether the telltale skin blisters are present, any newborn presenting with these non-specific signs of illness should be immediately evaluated for neonatal herpes.
How Neonatal Herpes is Contracted
The vast majority of neonatal HSV infections are acquired during the birthing process, known as perinatal transmission. This occurs when the infant comes into contact with the virus shedding from the mother’s genital tract during passage through the birth canal. The risk of transmission is highest if the mother experiences her first episode of genital herpes late in pregnancy, particularly during the third trimester.
A primary maternal infection acquired late in pregnancy is concerning because the mother has not yet developed protective antibodies to pass to the baby. Postnatal transmission, though less common, can occur if a baby is exposed to an active herpes lesion after birth, such as a cold sore on a caregiver. Transmission can happen through direct contact, like a kiss, or indirectly, such as touching an active lesion and then touching the baby.
In rare instances, the virus can be transmitted to the fetus while still in the womb, known as intrauterine infection. This occurs when the virus crosses the placenta to reach the fetus. However, transmission during delivery or from an external source after birth remains the primary concern.
Urgent Steps for Diagnosis and Treatment
If neonatal herpes is suspected based on any symptom, immediate transport to an emergency medical facility is imperative. Healthcare providers must begin a diagnostic workup and often initiate treatment immediately, even before the diagnosis is fully confirmed, due to the rapid progression of the disease. A full diagnostic evaluation includes swabbing any suspicious lesions, the mouth, eyes, and anus to test for the presence of the herpes simplex virus.
A lumbar puncture is also performed to collect cerebrospinal fluid (CSF), which is tested using Polymerase Chain Reaction (PCR) to determine if the virus has reached the central nervous system. Blood is also tested via PCR for viral DNA to look for signs of disseminated disease. The standard treatment involves the prompt administration of high-dose intravenous acyclovir, which is a powerful antiviral medication.
The duration of intravenous acyclovir treatment is based on the disease classification, typically lasting 14 days for localized SEM disease and 21 days for CNS or disseminated disease. Following the intensive intravenous therapy, infants who survive the infection are often placed on a six-month course of oral acyclovir to suppress the virus and improve long-term neurodevelopmental outcomes. This aggressive and timely treatment protocol significantly improves survival rates and limits the potential for long-term neurological damage.