Neonatal varicella, often called chickenpox in newborns, is a serious viral infection caused by the varicella-zoster virus (VZV). This condition can pose significant health challenges for infants due to their developing immune systems.
What is Neonatal Varicella?
Neonatal varicella refers to a VZV infection occurring within the first four to six weeks of a baby’s life. The varicella-zoster virus is a type of herpesvirus responsible for both chickenpox and shingles. While chickenpox is typically a mild illness in older children, it can lead to severe disease in infants.
Neonatal varicella differs from congenital varicella syndrome (CVS). CVS results from a maternal VZV infection during early pregnancy, specifically between 8 and 20 weeks of gestation, potentially leading to birth abnormalities. Neonatal varicella is acquired around the time of birth or shortly thereafter.
Mothers who have previously had chickenpox or been vaccinated typically transfer protective antibodies to their babies across the placenta. These maternal antibodies offer a degree of passive immunity. However, this protection is temporary and can decline rapidly, leaving infants susceptible to infection, with many becoming vulnerable as early as one to four months of age.
How Neonatal Varicella Develops and Its Signs
A newborn can contract varicella through transplacental transmission from a mother infected shortly before or after delivery, or through postnatal exposure to an infected individual. The highest risk for a severe form of neonatal varicella occurs when the mother develops the chickenpox rash between five days before and two days after delivery. During this narrow window, the infant is exposed to high viral loads without sufficient time to receive protective maternal antibodies.
The incubation period for VZV typically ranges from 10 to 21 days. If symptoms appear within the first 10 days of life, the infection was likely acquired before birth. Postnatally acquired infections usually show symptoms after day 13.
Signs of neonatal varicella include fever and irritability. The characteristic rash begins as macules (flat, red spots), progresses to papules (small, raised bumps), then to vesicles (fluid-filled blisters), and finally crusts over. This rash often appears first on the head and then spreads across the body.
Serious Health Risks
Neonatal varicella can be particularly dangerous for newborns because their immune systems are still immature, making them less equipped to fight off the virus compared to older children. The severity of the disease in newborns can vary, ranging from a mild illness to a widespread infection.
Serious complications can arise, including varicella pneumonia, an infection of the lungs causing significant respiratory distress. Encephalitis, an inflammation of the brain, can lead to seizures and rapid progression to a coma. Hepatitis, an inflammation of the liver, and disseminated disease, where the virus spreads throughout the body, also pose substantial threats.
The mortality rate for neonatal varicella is higher than for varicella in older children, with some estimates reporting rates up to 20-30% for infants whose mothers develop the rash close to delivery. Infants who experience severe complications may face long-term effects such as neurological problems or developmental delays.
Treatment and Prevention
Immediate medical intervention is often required for newborns diagnosed with varicella. Antiviral medications, such as acyclovir, are the primary treatment for VZV infections in high-risk populations like newborns. Acyclovir works by inhibiting viral replication and can help reduce the severity of the infection and the risk of complications. Experts generally recommend its use due to its established safety profile and effectiveness against herpesviruses.
Supportive care measures manage symptoms and promote recovery. These include ensuring the infant stays hydrated, managing fever with acetaminophen, and providing appropriate skin care for the rash to prevent bacterial superinfections. Hospitalization is often recommended for close monitoring, especially if there are concerns about the infant’s clinical status.
Preventing neonatal varicella involves protecting the mother and newborn from virus exposure. Maternal vaccination against varicella before pregnancy is effective in preventing maternal infection and reducing fetal transmission risk. For non-immune pregnant women exposed to VZV, Varicella-Zoster Immune Globulin (VZIG) may be administered, ideally within 96 hours of exposure, to help prevent severe maternal and potentially fetal infection.
For at-risk newborns, VZIG is recommended for post-exposure prophylaxis, especially for infants whose mothers develop varicella around the time of delivery (five days before to two days after). VZIG can help attenuate the infection, meaning it can make the disease less severe. Avoiding contact with individuals who have chickenpox or shingles is also advised for pregnant women and newborns to minimize exposure.