Chickenpox is caused by

Ans. A. Varicella-zoster virus. (Ref. Harrison's medicine 17th ed. Chapter 173)Varicella-zoster virus# Varicella-zoster virus (VZV) causes two distinct clinical entities:- varicella (chickenpox) and- herpes zoster (shingles).# Chickenpox, a ubiquitous and extremely contagious infection, is usually a benign illness of childhood characterized by an exanthematous vesicular rash.# 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.# Children between 5-9 yr age are most commonly affected.# Incubation period 14-17 days.# Secondary attack rate 72-90%.# Patients are infectious prior to onset of rash, during period of vesicle formation (4-5days) & until all vesicles are crusted.# Hallmark of infection is maculopapules, vesicles escabs in various stages.# Most common infectious complication of varicella is superficial bacterial infection of skin by Staph.# Most common extracutaneous site of affection by VZV is CNS.Recommendations for VZIG AdministrationExposure Criteria1. Exposure to person with chickenpox or zostera. Household: residence in the same householdb. Playmate: face-to-face indoor playc. HospitalVaricella: same 2- to 4-bed room or adjacent beds in large ward, face-to-face contact with infectious staff member or patient, visit by a person deemed contagiousZoster: intimate contact (e.g., touching or hugging) with a person deemed contagiousd. Newborn infant: onset of varicella in the mother <5 days before delivery or <48 h after delivery; VZIG not indicated if the mother has zoster2. Patient should receive VZIG as soon as possible but not >96 h after exposureCandidates (Provided They Have Significant Exposure) Include:1. Immunocompromised susceptible children without a history of varicella or varicella immunization2. Susceptible pregnant women3. Newborn infants whose mother had onset of chickenpox within 5 days before or within 48 h after delivery4. Hospitalized premature infant (>28 weeks of gestation) whose mother lacks a reliable history of chickenpox or serologic evidence of protection against varicella5. Hospitalized premature infant (<28 weeks of gestation or <1000-g birth weight), regardless of maternal history of varicella or varicella-zoster virus serologic status.