The varicella-zoster (V-Z) virus is a member of the herpes virus family. It is the cause of varicella (chickenpox), a viral infection that usually occurs early in childhood. The V-Z virus cannot live and reproduce anywhere other than in the human body.
Varicella is transmitted by direct contact and through respiratory droplets. For example, if someone who is infected coughs or sneezes and you inhale the droplets-which contain the virus-you can become infected (unless you already had chickenpox in the past). The virus is highly contagious; over 95% of susceptible patients become infected after exposure within the same household. Once you develop varicella, your immune system produces lifelong antibodies to combat it. (There is also a new vaccine for varicella-see below.)
One Virus, Two Infections.
The varicella-zoster virus causes both varicella and herpes zoster infection (shingles). You can get varicella only once-while your body fights the infection, it also develops immunity to the virus-but the virus itself remains dormant in your body. If reactivated, it can cause herpes zoster. In addition, if you've never had varicella, exposure to someone with herpes zoster can cause you to contract varicella. Herpes zoster is typically less severe than varicella, since the body already has antibodies against the virus. If herpes zoster infection occurs during pregnancy, it will not pose a major risk to either you or your baby unless you have a weakened immune system due to AIDS, cancer, or some other condition.
The incubation period for varicella is 10 to 14 days. In other words, it takes that long after being exposed to the virus for the characteristic chickenpox rash to appear. The rash consists of small, red spots, which evolve into raised, fluid-filled bumps, and then itchy blisters that crust over (scabs)-usually within a week. Typically, these sores appear first on the torso, then spread to the arms and legs, and sometimes to the face. Other symptoms of varicella include fever and malaise (not feeling well).
You are infectious beginning one day before the outbreak of the rash until all of the scabs have dried up and crusted over. It may take two weeks or so for these sores, which typically do not leave scars, to disappear.
In healthy children, varicella rarely leads to serious complications. However, in adults, two life-threatening illnesses may develop: encephalitis (infection and inflammation of the brain) and pneumonia (lung infection). Although less than 10% of varicella cases occur in patients over the age of 10, these older patients account for more than 50% of all deaths due to varicella.
Encephalitis occurs in less than 1% of pregnant women who develop varicella. Pneumonia is a far more common complication, developing in up to 20% of infected women during pregnancy. Before effective antiviral drugs were developed, nearly 40% of pregnant women with varicella pneumonia died from the illness.
A pregnant mother can transmit varicella to her baby via the placenta. Early in pregnancy, this can lead to birth defects, miscarriage, or fetal death, although the risk of these complications is less than 2%. The fetus may also contract congenital varicella if delivery occurs during maternal viremia, but before the development of maternal antibodies. Therefore, it is crucial to minimize your risk of infection during pregnancy.
Because of its characteristic sores, varicella is usually easy for your doctor to diagnose. If there is any doubt about this infection, your doctor may culture (grow in a laboratory) a specimen from one of your sores and analyze it under a microscope.
In some situations-such as if you are planning a pregnancy, are already pregnant, or have been exposed to chickenpox-your doctor may order a blood test to determine whether or not you are protected against the infection.