<prompt> Chickenpox is caused byVaricella-zoster virusEpstein-barr virusPox virusHerpes simplex virus  <response>: Ans. A. Varicella-zoster virus. Ref. Harrisons medicine 17th ed. Chapter 173Varicella-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. 