Varicella-Zoster Virus (Chickenpox)

Chickenpox (caused by the varicella-zoster virus) isone of the classic childhood diseases, and one of the most contagious. Nearly every unvaccinated child becomes infected with it. The affected child or adult may develop hundreds of itchy, fluid-filled blisters that burst and form crusts.

The infection rarely causes complications in healthy children, but it is not always harmless. Five out of every 1,000 children are hospitalized and, in rare cases, it can be fatal. Before the vaccination became widespread, chickenpox resulted in about 11,000 hospitalizations and 100 deaths a year.

This is a close-up picture of chickenpox. Early chickenpox lesions consist of small red papules which quickly fill with a yellowish or straw colored fluid to form small blisters (vesicles), as seen in this photograph. Later, these vesicles will rupture forming shallow erosions that crust over and then ultimately heal.

Click the icon to see an X-ray of pneumonia following exposure to chickenpox.

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Chickenpox can be especially severe in adults and very serious in anyone with a compromised immune system. In addition, the varicella virus (which persists after the childhood disease) erupts as a painful and distressing condition called herpes zoster (shingles) in about 20% of adults with a history of chickenpox. Chickenpox itself usually occurs only once, although a few cases of mild second infections, marked by the telltale rash, have been reported in older children years after their first infection.

Click the icon to see an image of the shingles.

Vaccines for Chickenpox