Chickenpox is a highly contagious disease caused by primary infection with varicella zoster virus (VZV).
It usually starts with vesicular skin rash mainly on the body and head rather than at the periphery and becomes itchy, raw pockmarks, which mostly heal without scarring. On examination, the observer typically finds skin lesions at various stages of healing and also ulcers in the oral cavity and tonsil areas.
Chickenpox is an airborne disease that spreads easily through coughing or sneezing of ill individuals or through direct contact with secretions from the rash. A person with chickenpox is infectious one to two days before the rash appears. They remain contagious until all lesions have crusted over (this takes approximately six days). Immunocompromised patients are contagious during the entire period as new lesions keep appearing. Crusted lesions are not contagious.
Chickenpox has been observed in other primates, including chimpanzees and gorillas.
The origin of the term chicken pox, which is recorded as being used since 1684, is not reliably known. It has been said to be a derived from chickpeas, based on resemblance of the vesicles to chickpeas, or to come from the rash resembling chicken pecks. Other suggestions include the designation chicken for a child (i.e., literally ‘child pox’), a corruption of itching-pox, or the idea that the disease may have originated in chickens. Samuel Johnson explained the designation as “from its being of no very great danger.”
Signs and Symptoms
The early (prodromal) symptoms in adolescents and adults are nausea, loss of appetite, aching muscles, and headache. This is followed by the characteristic rash and/or oral sores, malaise, and a low-grade fever that signal the presence of the disease. Oral manifestations of the disease (enanthem) not uncommonly may precede the external rash (exanthem). In children the illness is not usually preceded by prodromal symptoms, and the first sign is the rash or the spots in the oral cavity. The rash begins as small red dots on the face, scalp, torso and upper arms and legs; progressing over 10 – 12 hours to small bumps, blisters, and pustules — followed by umbilication and the formation of scabs,
At the blister stage, intense itching is usually present. Blisters may also occur on the palms, soles, and genital area. Commonly, visible evidence of the disease develops in the oral cavity and tonsil areas in the form of small ulcers, which can be painful and/or itchy. This enanthem (internal rash) can precede the exanthem (external rash) by 1 to 3 days or can be concurrent. These symptoms of chickenpox appear 10 to 21 days after exposure to a contagious person. Adults may have a more widespread rash and longer fever, and they are more likely to experience complications, such as varicella pneumonia.
Because watery nasal discharge containing live virus usually precedes exanthem (external rash) and enanthem (oral ulcers) by 1 to 2 days, the infected person actually becomes contagious one to two days prior to recognition of the disease. Contagiousness persists until all vesicular lesions have become dry crusts (scabs), which usually entails four or five days, by which time nasal shedding of live virus also ceases.
Chickenpox is rarely fatal, although it is generally more severe in adult men than in women or children. Non-immune pregnant women and those with a suppressed immune system are at highest risk of serious complications. Arterial ischemic stroke (AIS) associated with chickenpox in the previous year accounts for nearly one third of childhood AIS. The most common late complication of chickenpox is shingles (herpes zoster), caused by reactivation of the varicella zoster virus decades after the initial, often childhood, chickenpox infection.