Varicella (chickenpox) is a highly contagious disease caused by the varicella-zoster virus. The virus can be spread by respiratory droplets, such as from coughs or sneezes, or by direct contact, such as from blisters on the skin. Persons exposed to chickenpox may develop symptoms 10–21 days after they are exposed. The most common symptoms of chickenpox are rash (with blisters), fever, coughing, fussiness, headache, and loss of appetite.
Most people think of chickenpox as a mild disease — and, for most children, it is. Chickenpox usually lasts about one-and-a-half to two weeks and rarely causes complications. But the disease can be serious, especially in adults. There's no way to know which infected child or adult will develop a severe case.
In addition, years after having chickenpox, people can have shingles (also known as herpes zoster). Shingles is a more localized painful rash, often with blisters, on one specific area of the body. It can cause severe pain, which usually clears up in a few weeks or months but can last for years.
The chickenpox vaccine is a safe, effective way to prevent chickenpox and its possible complications. Two doses 3 or more months apart are recommended for all age groups. In the small number of cases when the vaccine doesn't prevent chickenpox completely, the infection is much milder than the infections that put most U.S. children into bed for a week years ago. (Source: