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Back to Infectious Diseases
Varicella Zoster
Chickenpox and shingles are caused by the same virus; varicella-zoster
(VZV). When a person, usually a child, is first exposed to the varicella-zoster
virus, he or she develops chickenpox, a highly contagious disease. Most
of us catch it during childhood because the virus can be spread through
air as well as through contact with the rash. The infection begins in the
upper respiratory tract where the virus reproduces over a period of 15 days
or more (the incubation period). The virus then spreads to the bloodstream
and migrates to the skin, giving rise to the familiar rash.
in some cases some of the virus particles leave the skin blisters and move
into the nervous system. There the viruses settle down in an inactive (latent)
form inside specific nerve cells. When the chickenpox virus reactivates,
the virus moves down the long nerve fibers that extend from the sensory
cell bodies to the skin. The viruses multiply, the telltale rash erupts,
and the person now has herpes zoster, or shingles.
Herpes zoster can occur in people who have never had a history of a "typical"
attack of chicken pox. In this situation the attack is subclinical and passes
undiagnosed. This is a possible explanation how someone with no history
of a typical attack of chicken pox can still develop zoster later in life
when the immune system is compromised.
Contact with a person with shingles may cause chickenpox (but not shingles)
in someone who has never had chickenpox before.
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Clinical manifestations
VZV causes 2 diseases:
- Chickenpox: a ubiquitous and extremely contagious infection, is usually
a benign illness of childhood characterized by an exanthematous vesicular
rash. The rash is centripetal arranged in crops and heals without scarring.
- Herpes zoster: zoster lesions (shingles). With reactivation of latent
VZV (which is most common after the sixth decade of life), herpes zoster
presents as a dermatomal vesicular rash, usually associated with severe
pain. The pain may continue after the rash subsides (post-herpetic neuralgia).
Diagnosis
Unequivocal confirmation of the diagnosis is possible only through the
isolation ofVZV in susceptible tissue-culture cell lines, the demonstration
of either seroconversion or a fourfold or greater rise in antibody titer
between convalescent- and acute-phase serum specimens, or the detection
of VZV DNA by polymerase chain reaction (PCR).
Treatment
Medical management of chickenpox in the immunologically normal host is
directed toward the prevention of avoidable complications.
Patients with herpes zoster benefit from oral antiviral therapy, as evidenced
by accelerated healing of lesions and resolution of zoster-associated pain
with acyclovir, valacyclovir, or famciclovir.
A live attenuated varicella vaccine has been licensed and is recommended
for administration to all immunocompetent children and adults at risk of
infection.
Immune prophylaxis can consist of the administration of specific zoster
immune globulin (ZIG) derived from patients with herpes zoster, varicella-zoster
immune globulin (VZIG), or the intravenous formulation of zoster immune
plasma (ZIP).
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