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VARICELLA (CHICKEN POX)



VARICELLA (CHICKEN POX)
Virology:
Varicella zoster virus (VZV), included in the family Herpesviridae
Epidemiology:
Varicella zoster virus infection occurs worldwide. Seroprevalence
at age 20 is typically 95%. Primary infection with VZV causes
chickenpox, which is primarily a disease of childhood, although
it may occur at any age and is more severe in adults, with a
higher incidence of serious complications such as pneumonitis.
Reactivation of latent VZV in sensory ganglia causes herpes
zoster (shingles). The absolute incidence of zoster is higher in
adults, but not if corrected for prior exposure to VZV.
Reservoir: Man

Mode of Transmission:
Person-to-person, by direct contact or droplet spread from
cases of chicken pox or herpes zoster.
Incubation Period:
13–21 days.
Infectious Period:
From 2 days before the onset of rash until the lesions are
crusted. Scabs are noninfectious.
1-Fetal Infection
If infection occurs at less than 26-weeks gestation, there is a
small risk of fetal malformation (microcephaly, hydrocephalus,
limb hypoplasia, cutaneous scarring and ophthalmic defects).
The risk is highest during the first trimester (3%). Infection just
before or shortly after delivery may be followed by neonatal
infection, which can be severe.
2-Infection in Neonates
Neonates of mothers who develop varicella <5 days before or
shortly after delivery will not be protected by maternal IgG
and may develop severe disseminated infection. They should
receive VZIG (see below) and be monitored for 14–16 days
for signs of infection, which should be treated promptly with
aciclovir. Some recommend prophylactic acyclovir for these
neonates. Herpes zoster during pregnancy poses no threat to
mother or child, since by definition, the mother will have anti-
VZV IgG and this will protect the neonate.
Clinical Features:-
• There is a mild prodrome of malaise, fever, headache and
rhinitis.
• The rash develops as crops of vesicles each
appearing on an erythematous base (“dewdrop on a rose
petal”).Vesicles rapidly progress to umbilicated papules,
pustules and scabs. Distribution is typically central
on head, trunk and arms, and also the palate or gums. New
crops continue to appear for up to 7 days. Fever remains
elevated for 4–5 days after onset of rash.
Pulmonary disease during varicella is often due to
secondary bacterial pneumonia, usually with Streptococcus
pneumoniae, Haemophilus influenzae or Staphylococcus
aureus. Staphylococcal septicemia may occur.
 Investigations:
Light Microscopy of Vesicle Contents
Reveals multinucleate giant cells (Tzanck preparation);
electron microscopy shows large numbers of herpes virus
particles. Methods are available for the rapid detection of
VZV antigens in vesicle fluid. Retrospectively diagnosis can be
confirmed by serology.
CXR
CXR shows widespread patchy shadowing; may show military
mottling. Residual pulmonary fibrosis and CXR calcifications
may occur in survivors.
Differential Diagnosis:
Infectious vesicular rashes include:
– Herpes simplex infection
– Hand, foot and mouth disease
– Disseminated gonococcal infection
Noninfectious causes include:
– Stevens-Johnson syndrome
– Pemphigus
– Pemphigoid
In atypical cases, vesicular impetigo due to Staphylococcus
aureus or GAS can be confused.
Treatment:
Supportive Care
• Antipyretic paracetamol and non-aspirin drug
• Plenty of fluid intakes
• Soothing agents like lotion calamine over the affected skin
• Antipruritic: In troublesome itching condition.
Antiviral Treatment (Not Usually Required)
Aciclovir shortens and reduces the severity of illness but
must be given early (ideally <24 hours) to have a significant
effect. Aciclovir is not recommended for routine use in
immune-competent children. Intravenous acyclovir is indicated
in the following circumstances:
• Immuno-compromised patients (including those with AIDS)
• Neonates and if there is evidence of severe or disseminated
disease (30 mg/kg in three divided dose IV for 10 days)
• In particular, ophthalmic disease, pneumonitis or
encephalitis.
Complications:
• Bacterial super-infection of the rash is common Streptococcus
followed by Staphylococcus, sepsis, scarlet fever. In severe
cases, varicella gangrenosum (Streptococcus)
• Hemorrhagic chickenpox
• Many patients have mild hepatitis
• Mucositis may cause dysuria
• Varicella pneumonitis is more common in immune-compromised
patients
• It may progress rapidly, with hypoxia and tachypnea
• Encephalitis (cerebellitis): Chickenpox cerebellitis is an
important cause of acute ataxia in children with good
prognosis
Other CNS complications:
– GBS
– Transverse myelitis
• Thrombocytopenia and disseminated intravascular
coagulopathy: Occur very rarely and may cause hemorrhagic
varicella, with bleeding into vesicles. All complications are
commoner in the immune-compromised.
Prevention:
Chicken pox is very contagious.
• Isolation
• Rest at home to keep away from close human contact until
the lesions are crusted.
Vaccination:
Live attenuated varicella-zoster virus (Oka strain), obtained
from human diploid cell culture.
Indications
• A single dose of vaccine is recommended in children ≥12
months of age. For children ≥12 years, 2 doses at 4-week
interval. Currently, however, 2 doses are recommended
irrespective of age after 12-month age
• For active immunization, from age 12 months onwards at
a dose of 0.5 mL, to be given subcutaneously
• Varicella and MMR vaccine can be given in same date at
different sites, if not given they should be given at 4-weeks
interval. They can be given combined by single injection
MMRV vaccine at 12 months of age through 12 years of age.
This MMRV vaccine may be used both first and second dose
of MMR and varicella vaccine. Breakthrough infection may
occur after first dose of varicella vaccine and manifests as
modified chickenpox (milder form).
Contraindications
• Acute severe febrile illness
• Lymphocyte count <1200/cumm.)
Adverse Effects
• Local reaction (pain, erythema)
• Generalized rash (maculopapular).

VARICELLA (CHICKEN POX)

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