Transmission is most likely within the first two days before the appearance of the rash. Chickenpox is contagious for up to five days of the rash but not after day 6 and generally, children can go back to school after this time. Many people contract chickenpox during childhood or adolescence, but adults who have escaped the infection earlier will at some time or the other get infected. Chickenpox infection then can be severe and lead to complications. The most obvious is the blistered and highly itchy rash, which can last for up to 10 days.
Fever is probably the most common clinical sign along with chills, nausea and vomiting.
Although for many children chickenpox does not produce major health problems, complications can develop in some cases, especially pneumonia, which may be fatal . Bacterial superinfection of the skin is generally seen in healthy children under 5 years of age and can sometimes lead to unsightly scarring, which may cause cosmetic concerns later in life. Chickenpox is more serious in adolescents and adults than in children. The fever is higher and continues for much longer and the rash is much heavier. Mortality also tends to be higher when varicella is contracted later in life.