Chicken pox, also spelled chickenpox, is a common childhood disease caused by the varicella-zoster virus (VZV), also known as human herpesvirus 3 (HHV-3). It is characterized by a fever followed by itchy raw pox or open sores. It is rarely fatal: if it does cause death, it is usually from varicella pneumonia, which occurs more frequently in pregnant women. In the US, 45% of chicken pox deaths were in the under-20 age group. Chicken pox has a two week incubation period and is highly contagious by air transmission two days before symptoms appear. Therefore chicken pox spreads quickly through schools and other places of close contact. As the disease is more severe if contracted by an adult, parents have been known to ensure that their children became infected before adulthood.
Later in life, virus remaining in the nerves can develop into the painful disease, shingles. A chicken pox vaccine is now available, and is now required in some countries for children to be admitted into elementary school. In addition, effective medications (e.g., acyclovir) are available to treat chicken pox in healthy and immunocompromised persons.