Chickenpox is caused by the human alpha herpes virus 3 and is transmitted through air droplets or direct contact with infected individuals. It has an incubation period of 14-16 days and is communicable from 1-2 days before until 4-5 days after the appearance of the rash. The live attenuated chickenpox vaccine provides over 90% protection against the disease.

1. DR ATHAR KHAN - LCMD
CHICKEN POX
DR ATHAR KHAN
LIAQUAT COLLEGE OF MEDICINE AND DENTISTRY
Synonym:
‘Varicella’
Causative organism
Human (alpha) herpes virus Chicken pox 3
Source of infection:
Case (person-to-person contact)
Incubation Period (IP)
14 – 16 days
Mode(s) of transmission
Air droplets (respiratory), Droplet infection (droplet nuclei)
Louis Pasteur:
– Developed ‘vaccines for Chicken pox’
CFR for Chicken pox < 1%
CFR represents ‘killing power of a disease”. It is ‘closely related to virulence of
organism.
Types of Epidemics – Chicken Pox
Single exposure or ‘Point source’ epidemics
Secondary Attack Rate (SAR)
90%
SAR: no. of exposed persons developing the disease within range of incubation period
(IP), following exposure to the primary case

2. DR ATHAR KHAN - LCMD
Duration of isolation
6 days after onset of rash
Isolation: Separation for the period of communicability of persons/ animals from others
to prevent disease transmission
Period of Communicability
1 – 2 days before to 4 – 5 days after appearance of rash
Late complication of chicken pox:
Shingles
Most rapid and sensitive means of diagnosis:
Examination of vesicle fluid under electron microscope (shows round particles)
Congenital Varicella:
Most threatening if transmitted in 1st trimester of pregnancy

3. DR ATHAR KHAN - LCMD
Chicken pox Vaccine:
- Live attenuated
– Strain: OKA strain
– Seroconversion : >90%
Varicella Zoster immunoglobulin (VZIG):
– Given within 72 hours of exposure
– Dose: 1.25 – 5.0 ml intramuscularly
– Reserved for:
– Immunosuppressed contacts of acute cases
– Newborn contacts