What Is Varicella-Zoster Virus (VZV)?

The varicella-zoster virus (VZV) is a member of the herpes virus family. It can cause chickenpox and shingles. The VZV can’t live and reproduce anywhere other than in the human body.

The virus is highly contagious and spreads easily from one person to another. It’s transmitted through direct contact with infected respiratory droplets. This can occur by touching a surface contaminated with the droplets or by inhaling the droplets when an infected person coughs or sneezes near you. Once you become infected with the virus, your immune system produces lifelong antibodies to combat it, which means you can’t contract the virus again. There’s also a new vaccine that can protect you from a VZV infection.

Many pregnant women have already been exposed to the virus and are therefore immune. However, those who have never had the infection or been immunized are at an increased risk for complications if they become infected with VZV. The virus can potentially cause birth defects or illness in the baby, so doctors often order blood tests to screen for VZV in pregnant women who aren’t immune to the virus. These tests are usually performed before or early in pregnancy. If the virus is detected, treatment can help prevent or weaken the severity of the illness.

One Virus, Two Infections

VZV can cause chickenpox, which is also called varicella, and shingles, which is also called herpes zoster. Varicella is a common childhood illness that causes an itchy, blister-like rash on the skin. You can get varicella only once. As your body fights the infection, it develops immunity to the virus.

However, the virus itself remains dormant in your body. If the virus is reactivated, it can emerge as herpes zoster. Herpes zoster is characterized by a painful rash with blisters. It’s typically less severe than varicella because the body already has antibodies against the virus. It’s important to note that herpes zoster doesn’t spread from one person to another. If someone who has never had chickenpox comes into contact with the fluid from shingles blisters, they’ll develop chickenpox instead of shingles.

What Are the Symptoms of the Varicella-Zoster Virus?

The incubation period for VZV is 10 to 14 days. This is the amount of time it takes for symptoms to appear after being exposed to the virus. The typical rash of varicella initially consists of small, red spots. These spots eventually evolve into raised, fluid-filled bumps, and then into itchy blisters that crust over. The rash typically starts on the face or torso and quickly spreads to the arms and legs. Other symptoms of varicella include fever, fatigue, and headache. People with varicella are contagious beginning one to two days before the rash appears and until all of the blisters have formed crusted over. It may take two weeks or longer for these sores to disappear.

If varicella becomes active again, the virus can emerge as herpes zoster. This virus causes a red, painful rash that may appear as a stripe of blisters on the torso. The clusters of blisters typically appear one to five days after the rash develops. The affected area may feel itchy, numb, and very sensitive. Other symptoms of herpes zoster may include:

  • a fever
  • general discomfort
  • muscle aches
  • a headache
  • swollen lymph nodes
  • upset stomach

What Complications Can the Varicella-Zoster Virus Cause During Pregnancy?

Susceptible pregnant women are at risk for certain complications when they contract varicella. Approximately 10 to 20 percent of those infected with varicella develop pneumonia, a severe lung infection. Encephalitis, or an inflammation of the brain tissue, may also occur in a very small number of pregnant women with varicella.

A pregnant mother can transmit varicella to her baby via the placenta. The risks to the baby depend on the timing. If varicella develops during the first 12 weeks of pregnancy, the baby has a 0.5 to 1 percent risk of developing a rare birth defect known as congenital varicella syndrome. If the virus is contracted between weeks 13 and 20, the baby has a 2 percent risk of having birth defects.

A baby with congenital varicella syndrome might have underdeveloped arms and legs, eye inflammation, and incomplete brain development. The baby may also contract congenital varicella if delivery occurs while the mother is still infected and hasn’t yet developed antibodies to the virus. If varicella develops within five days or within one to two weeks after delivery, the baby might be born with a potentially life-threatening infection called congenital varicella.

Due to the potential risks, it’s critical for you to minimize your risk of infection if you’re pregnant. You can do this by getting screened for VZV so you can take the necessary precautions. If you’re exposed to varicella during pregnancy and you aren’t immune, you must call your doctor immediately. They may be able to give you an injection of varicella-zoster immune globulin (VZIG), a product that contains antibodies to VZV. When given within 10 days of exposure, VZIG can prevent varicella or reduce its severity. It can also help reduce the risk of complications for you and your baby.

How Can the Varicella-Zoster Virus Be Prevented?

Ask your doctor about the varicella vaccine if you’re considering pregnancy and haven’t already had chickenpox or been immunized. Though the vaccine is safe for adults, it’s recommended that you wait until three months after your second dose before trying to conceive. If you’re not sure whether you’re immune to varicella, ask your doctor to perform a blood test. The test can determine whether you have antibodies to the virus. There’s also a vaccine for VZV, but it’s only been approved for use in adults over age 50. It’s important to avoid those with chickenpox, including daycare centers and school settings, where children may not be vaccinated, and often exposed.