This topic is a part of Epidemiology of Communicable Diseases. It further falls into the category of respiratory infections. This topic covers important points from Park textbook of Preventive and Social Medicine about chickenpox.

3. 1. AGENT FACTORS
AGENT: Varicella Zooster Virus (Human alpha herpes
virus 3).
SOURCE OF INFECTION: Oropharyngeal secretions
+ lesions of skin and mucosa.
INFECTIVITY: 2 days from appearance of rash till 5
days thereafter.
SECONDARY ATTACK RATE: highly communicable.
The secondary attack rate in household contacts
approaches 90%.

4. AGE: Children under 10 years are at greater risk.
IMMUNITY: 1 attack gives lifelong immunity. 2nd attacks
are rare.
PREGNANCY: From pregnant mother to child leading
to congenital Varicella.

5. TIME: More prevalent during winter season.
PLACE: More common in overcrowded areas.
PERSON: More common in people with poor personal
hygiene.

6. A. DIRECT: droplet infection + droplet nuclei.
B. TRANSPLACENTAL: from pregnant mother to
child leading to congenital Varicella.
5. RESERVOIR OF INFECTION
Infected person
6. PORTAL OF ENTRY
Upper respiratory tract.
7. INCUBATION PERIOD
14-16 days.

7. Clinical spectrum of chickenpox may vary from
mild illness to severe febrile illness with
widespread rash.
STAGES
A. PRE-ERUPTIVE STAGE:
Sudden onset
Mild or moderate fever
Backache
Malaise
This stage lasts about 24 hours in children and 2-3
days in adults.

8. Rash is often the 1st sign in children coming on the
day the fever starts.
CHARACTERISTICS OF ERUPTION:
a). DISTRIBUTION:
Centripetal
Symmetrical
Appears 1st on trunk, then on face, arms and legs
Mucosal surfaces
Diminishes centrifugally

9. Rash advances quickly through the stages of
macule, papule, vesicle, and scab.
Dewdrop like vesicles present on the skin
containing clear fluid with easily ruptured walls,
surrounded by an area of inflammation.
Vesicles may form crusts without going through
pustule stage.
Scabbing begins 4 to 7 days after the rash
appears.

11. All stages of rash may be seen simultaneously at
one time in the same place.
This is due to rash appearing in successive crops
for 4-5 days in the same area.
d). FEVER:
Does not run high.
Shows exacerbations with each fresh crop of
eruption.

12. Hemorrhages
Pneumonia
Encephalitis
Acute cerebellar ataxia
Reye’s syndrome
Fetal deaths and birth defects in case of
maternal varicella during pregnancy.

13. Rarely required as clinical signs are usually clear-
cut.
Lab confirmation by detecting VZV DNA using
PCR.
Direct immunofluorescence for rapid testing.

14. No special treatment of chickenpox.
CONTROL MEASURES:
Notification to health authorities.
Isolation from school for only 1 week after
eruption first appears.
Contact with susceptible is avoided.
Disinfection of the articles.
Child should be kept under observation for 21
days.

15. A). IMMUNOGLOBULINS:
Varicella Zooster Immunoglobulin 1.25-5ml I/M
given within 72 hours of exposure has been
recommended for prevention.
B). VACCINE:
Live attenuated varicella virus vaccine is safe and
effective in preventing the disease.
Should not be given to immunocompromised
individuals and pregnant women.
Contraindicated in persons allergic to neomycin.

16. The 2 diseases are now regarded as different
host responses to the same aetiological agent
which is VARICELLA ZOOSTER VIRUS.
Herpes Zooster is a result of proliferation of
varicella virus in cranial or spinal nerves
producing pain and a vesicular eruption in the
innervated area.
It could be either a reinfection with the virus or
a reactivation of a latent virus.

18. An acute infectious disease caused by
VARIOLA VIRUS and clinically characterized
by a sudden onset of fever, headache,
backache, vomiting and sometimes
convulsions especially in children.
On the 3rd day of fever, a typical rash appears
which is centrifugal in distribution and passes
through successive stages of macule, papule,
vesicle, pustule, and scab with subsequent
scarring.

19. Previously, it was one of the greatest killer
disease.
WHO declared on 8th May, 1980 that small
pox has been eradicated globally.
See case definitions from Park.