The red rash that most people can identify as chickenpox is the second stage of the disease. 24-48 hours before these symptoms appear, the infected person may experience a fever of about 100°--102° Fahrenheit. Other symptoms may include sore throat, abdominal pain, headache, or a general feeling of being sick. There is no way to know that chickenpox will develop unless it is known that the child has been around other infected children or immediate testing is done.
Though a parent generally can't know if the child is sick with flu, another virus or chickenpox in the early stages, the disease is very contagious from generally about 48 hours before the rash appears until all the red blisters are crusted over and in the healing stage. The virus can be spread through the air or by contact with fluid from chickenpox blisters. The disease usually lasts about a week, and children are generally asked to stay out of school about two weeks to be sure the infection is completely gone.
Chickenpox is generally found most in children, though a vaccine was created and educational efforts informed parents of the importance of getting both the shots (generally at 12-15 months old) and booster shots (at 4-6 years old). The Centers for Disease Control (CDC) also make an effort to have people 13 years of age and older who have never had chickenpox get the vaccine. The CDC states that about 11,000 people per year were hospitalised in the United States for chickenpox before the vaccine was introduced.
Chickenpox is caused by the varicella-zoster virus, which is a herpes-type virus that also causes shingles and postherpetic neuralgia in adults. Though the chickenpox virus may go into remission in a child, it generally stays within the body, and in about 10-20 per cent of infected children, it reappears in adult life.
After infection, the well-known red, itchy rash generally appears first on the stomach, back, or face. It is generally less than a quarter of an inch wide and can become worse with children who have skin disorders like eczema. From the initial breakout, the rash can spread throughout the body, including the ears, mouth, scalp, nose, and genitals. The bumps begin to appear as small pimples. They grow into thin-walled blisters filled with pus. These eventually break, crust over and become a scab.