<prompt> The infectivity of chicken pox lasts for -Till the last scab falls off6 days after onset of rash3 days after onset of rashTill the fever subsides  <response>: Chicken poxCausative agent Varicella zoster virus Herpes simplex type III.Portal of entry Respiratory tract or conjunctivaI. P. 10-21 days.Infectious period 2 days before and 5 days after the onset of rash.Secondary attack rate is high 90 Age group 5-9 Yrs.CFs - has two stages1. Pre-eruptive stagefever, back pain, malaise, shivering2.Eruptive stageRash is symmetrical, mostly on flexor surface.Centripetal in distributionMainly On trunk, less common on arms and legPalms and soles are not usually affectedThere is rapid evolution of rashRash is plemorphic, that is, all stages of rash Papule, vesicle and crusts may be seen simultaneously.Disease is more severe in adults than in children. 