Chickenpox, or also known as varicella, is a very common contagious illness. It’s most common in children, but can also occur in adults. Chickenpox or also known as varicella is a very common contagious illness. It’s caused by a type of herpes virus and it’s most contagious from 2 to 3 days even before the rush develops until blisters are crusted over. Children are more exposed to this contagious illness and usually it’s nothing serious. However, if some pregnant women, adults or teenagers have weak immune system, chickenpox can become very serious. The incubation period for chickenpox is generally between 14 to 16 days, but it can also be between 10 to 21 days. That is actually the period from your exposure to the actual symptoms from the varicella. The symptoms from this contagious illness are: feeling ill, fever, and of course, a rush all over the body with blisters filled with fluid which burst and crust over after few days. However, new blisters appear for up to a week. You should know that an infected person can spread the chickenpox without even knowing it, because he may not even have any symptoms yet. There is a vaccine for children and teens which prevents chickenpox. It’s also recommended for adults who have not had varicella. But if you catch this virus, the only thing you could do is prevent yourself from scratching the rush and try to relieve the discomfort and the fever.