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Varicella is a viral illness caused by an organism called the varicella-zoster virus. In many countries, including the United States, Canada and the United Kingdom, this illness is known as chickenpox. The infection normally is mild, with symptoms that persist for 10 to 14 days. After a person contracts varicalla once, he or she typically becomes immune to it.
The varicella virus is highly infectious and can be spread through exposure to coughing or sneezing by an infected person, as well as by direct contact. Another factor that increases the ease of transmission is the fact that a person who contracts chickenpox is infectious before he or she begins to show symptoms. Once someone has been exposed to the virus, he or she will develop symptoms in 10 to 21 days, but the infectious period begins five to seven days earlier. The infectious period lasts another five to 10 days after symptoms appear.
In adults, the first symptoms of infection are nonspecific and include nausea, fever, headache, general muscle pain and loss of appetite. The characteristic itchy rash associated with chickenpox begins to develop shortly thereafter. In children, the rash might develop before or concurrently with other symptoms. Blisters first develop on the head and body, then spread to the limbs. New blisters continue to form for up to five days, and by the sixth day, the oldest blisters will have begun to heal. Most blisters heal within two weeks of the rash first appearing.
Treatment for the infection generally consists of management of the symptoms with medication to reduce itching, pain and fever. Both children and adults can be treated with antiviral medications such as acyclovir to reduce the severity of symptoms. No further treatment is needed unless complications develop.
Complications of varicella are rare, but they can be severe and potentially life-threatening. Complications might develop if blisters become infected or if blisters develop in a sensitive location, such as the eye. The least common, and most severe, complications are pneumonia and encephalitis, which are infection and inflammation of the lungs and brain, respectively.
If the virus is contracted by a woman who is pregnant, the virus might cross the placental barrier and infect the fetus. Depending on the stage of pregnancy at which this occurs, the effects of fetal infection might include damage to the eyes, spinal cord or brain, skin disorders and anal or bladder dysfunction. A pregnant woman who becomes infected toward the end of her pregnancy is at risk of premature delivery, and if the child is exposed at or after birth, he or she is at risk of pneumonia and other complications.
The varicella immunization is part of the vaccination schedule for children in many countries, including the U.S., Australia and New Zealand. In immunized populations, infection is relatively rare; globally, however, as many as 90 million people are infected annually. In countries where children are not immunized, almost all children will contract the infection.