Chickenpox is the infection with the highest rate of transmission, which is why it is called an 'outbreak'. The virus that causes the disease is called Varicella Zoster Virus (VZV). The signs and symptoms of this disease vary. In adults, it is characterized by a rash, fever, fatigue, and headache. Usually, the symptoms appear a week after exposure to the virus. However, in adults, the duration can vary from one day to two weeks.

People who were infected by the virus as a child are protected for the rest of their lives. Some adults can get this infection again, but they are only protected for a Chickenpox short period of time. Chickenpox can occur at any age, but it is more common in children.

Adults who have had the chickenpox, even once, are also more susceptible to this disease later in life. When an adult gets chickenpox, the virus remains in the nerve ganglia for the rest of his/her life. Chickenpox is usually a mild condition in children, although it can be very severe.

In adults, however, it can cause complications such as pneumonia, encephalitis (inflammation of the brain), or even death. Most people recover from this illness within a few weeks.