Chickenpox epidemiology and demographics
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
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Overview
Epidemiology
Primary varicella is an endemic disease. Cases of varicella are seen throughout the year but, like other viruses spread by the respiratory route eg. measles and rubella, they are seen more commonly in the winter and early spring. This is unlike that for enteroviruses and lends some support to the view that varicella is spread mainly by the respiratory route. Herpes zoster, in contrast, occurs sporadically and evenly throughout the year. Varicella is one of the classic diseases of childhood, with the highest prevalence occurring in the 4 - 10 years old age group. Like rubella, infection is uncommon in preschool children. Varicella is highly communicable, with an attack rate of 90% in close contacts. Most people become infected before adulthood but 10% of young adults remain susceptible. However, this pattern of infection is not universal, eg. in rural India, varicella is predominantly a disease of adults, the mean age of infection being 23.4 years. It was suggested that this could be due to interference by other respiratory viruses that the children are exposed to at an early age.[1]
Historically, varicella has been a disease predominantly affecting preschool and school-aged children. Although mostly noted in preschool and primary levels, the said disease has also been noticed among adults, with the pocks being darker and the scars more prominent than their younger counterparts.[1]