• An acute, highly infectious disease
caused by Varicella-zoster Virus. It is
characterized by vesicular rash that may
be accompanied by fever and malaise.
• Agent: V-Z virus.
• Source of infection: A case of chicken
pox. Oropharyngeal secretion and
lesions of skin & mucosa.
• Chicken pox is highly communicable.
• Host factors: Age- primarily in
children under 10 years. The
disease can be severe in adults.
• Environmental factors: During
first six months of year.
• Transmission: Droplet infection.
Can cross placental barrier and
may cause Congenital Varicella.
• Incubation period: 14-16 days.
• Pre-eruptive stage: Mild/moderate
fever, pain in back, shivering and
malaise. This stage is very brief, lasting
about 24 hours. In adults last for 2-3
• Eruptive stage: In children, rash is often
the first sign. It comes on the day the
• Distribution: Rash is symmetrical. First
appears on the trunk where it is abundant,
then comes to the face, arms and legs.
Mucosal surfaces (buccal, pharyngeal) are
affected. Axilla may be affected, but palms
and soles are usually not affected.
• Rapid evolution: advances quickly through
macule, papule, vesicle and scab. Vesicles
filled with clear fluid look like ‘dew-drops’ on
• Pleomorphism: Characteristic feature of
chicken pox. All stages of rash ( papules,
vesicles and crusts) may be seen
simultaneously at one time, in the same area.
• Fever: Not high, but shows exacerbation with
each fresh crops of eruption.
Differences between small pox and
chicken pox (Park)
Palms and soles are affected
Rash prominent on extensor
surfaces and bony prominences
Vesicles multilocular and
Palms and soles are not
Mostly on flexor surfaces
Unilocular- Dew drop
Complications of chicken pox:
• Mild, self limiting disease.
• Complication may occur in
immunosuppressed, may also in normal
children and adults.
• Hemorrhage, Pneumonia, encephalitis, acute
cerebellar ataxia, Reye’s syndrome
• Infection during pregnancy may cause fetal
wastage and birth defects.
Prevention and control:
• No specific treatment for chicken
pox. The usual control measures are
notifications, isolation of cases and
disinfection of articles
• Varicella Zoster immunoglobulin
(VZIG)- for immunosuppressed and
• Vaccine- live attenuated vaccine.