<P> Chickenpox occurs in all parts of the world . In 2013 there were 140 million cases of chickenpox and herpes zoster worldwide . Before routine immunization the number of cases occurring each year was similar to the number of people born . Since immunization the number of infections in the United States has decreased nearly 90% . In 2015 chickenpox resulted in 6,400 deaths globally--down from 8,900 in 1990 . Death occurs in about 1 per 60,000 cases . Chickenpox was not separated from smallpox until the late 19th century . In 1888 its connection to shingles was determined . The first documented use of the term chicken pox was in 1658 . Various explanations have been suggested for the use of "chicken" in the name, one being the relative mildness of the disease . </P> <P> The early (prodromal) symptoms in adolescents and adults are nausea, loss of appetite, aching muscles, and headache . This is followed by the characteristic rash 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, upper arms and legs; progressing over 10--12 hours to small bumps, blisters and pustules; followed by umbilication and the formation of scabs . </P> <P> 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 or itchy or both; 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 . </P> <P> Because watery nasal discharge containing live virus usually precedes both exanthem (external rash) and enanthem (oral ulcers) by 1 to 2 days, the infected person actually becomes contagious one to two days before 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 ceases . </P>

Where did the chicken pox virus come from