Varicella (Chickenpox) -

             Varicella-Zoster Virus

             Dr Sampurna Roy MD

 Infectious Disease Online




Varicella (chickenpox) is an acute vesicular exanthem caused by the varicella-zoster virus, an agent that has a worldwide distribution and for which humans are the only known host.  There are no animal reservoirs.

VZV (HHV3) is a neurotrophic alpha-herpesvirus. 

Visit:Herpes Simplex Virus Infection ;Herpes Zoster(Shingles) ;Smallpox

VZV is named after : Varicella, an alternative name for chickenpox (the primary VZV infection) Zoster, another name for shingles (reactivation of latent VZV infection).

Although all age groups are susceptible, in temperate zones chickenpox affects mostly children and in the tropics mostly young adults.


The virus, which is spread through inhalation of droplets or by direct contact is highly contagious from about 24 hours before the initial eruption to a week of more thereafter.


Although infection with varicella-zoster virus establishes lifelong immunity and chickenpox does not recur, the latent viral genome may be activated years later to cause shingles.

Nonimmune persons (usually children) are susceptible to primary infection with varicella-zoster virus.

Chickenpox begins as a “silent” infection of the nasopharynx, with local replication of varicella-zoster virus.

After an incubation period of 10 to 23 days, the virus enters the bloodstream, causing viremia and a sudden onset of fever, malaise, and anorexia.    Image Link

In the circulation it seeds reticuloendothelial cells, an effect that leads to secondary waves of viremia.

The virus then disseminates to skin and viscera, and within 24 hours a red maculopapular eruption develops, usually on the upper trunk and face.

The papules rapidly become clear vesicles with an erythematous base.

In the next 24 hours, the vesicles become cloudy, the eruption begins to itch, and scratching may rupture the vesicles.

Separate crops appear for 3 to 6 days and spread peripherally.

After the last crop, the scabs heal withour scarring.

Though vesicles of the skin are generally painless, painful lesions may develop on mucous membranes, such as the cornea and tympanic membrane.

Complications include pneumonia, encephalitis, hepatitis, carditis, keratitis, orchitis, arthritis, hemorrhages and acute encephalopathy with fat accumulation in the viscera (Reye’s syndrome).

Histologically, the skin lesions initially show ballooning of epidermal cells.

Later, unilocular vesicles containing proteinaceous fluid, degenerating cells and syncytial giant cells are seen.

Cowdry type A intranuclear inclusions are seen in epidermal cells, endothelial cells of superficial capillaries, reticuloendothelial cells, and fibroblasts.

The affected organs in chicken pox exhibit spherical foci of coagulative necrosis.

At the margin of these necrotic foci, surviving cells contain intranuclear inclusions.

Visit: Chickenpox


Reports of chicken pox in area

Doctors intentionally Giving kids Chicken Pox a Bad Idea

Varicella-Zoster Virus Infection Triggers Formation of an Interleukin-1β (IL-1β)-processing Inflammasome Complex


Ultra-violet radiation is responsible for the differences in global epidemiology of chickenpox and the evolution of varicella-zoster virus as man migrated out of Africa

Chickenpox, chickenpox vaccination, and shingles

Household size is critical to varicella-zoster virus transmission in the tropics despite lower viral infectivity

Declining incidence of chickenpox in the absence of universal childhood immunisation

Chickenpox Exposure and Herpes Zoster Disease Incidence in Older Adults in the U.S.

Chickenpox at Ninety Four: A Case for Extending the Use of Varicella Vaccine in the UK

Facts about chickenpox


Isolated bilateral anterior optic neuritis following chickenpox in an immunocompetent adult.Neurol Sci. 2006 Sep;27(4):278-80.

Varicella.Lancet. 2006 Oct 14;368(9544):1365-76.

Acute hemiparesis after chickenpox.Ugeskr Laeger. 2006 Jun 5;168(23) :2261-2

One dose of varicella vaccine does not prevent school outbreaks: is it time for a second dose?Pediatrics. 2006 Jun;117(6):e1070-7

Enhanced chickenpox exanthema in vaccine injection site.Scand J Infect Dis. 2006;38(10):920-1.

Optic neuritis in herpes zoster ophthalmicus. Jpn J Ophthalmol. 2000 Sep-Oct;44(5):550-4

Pre-eruptive varicella encephalitis: case report and review of the literature.Eur J Pediatr. 1998 Oct;157(10):814-5.

Leukoencephalitis with hemiplegia during chickenpox.Arch Pediatr. 1997 Nov;4(11):1100-2

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