A Child (Girl) is suffering from varicella (fever & rash) & and child's aunt is pregnant. What is the earliest time, she can meet her aunt:

Ans: A (When the lesions have crusted) The crusts from chicken pox lesions donot contain viable virus and are therefore not infective."The period of infectivity lasts from 24-48 hrs before the rash until all the vesicle are crusted (the scab are not infective unlike small- pox"- O.P Ghai 7th /186Differences between smallpox and chickenpoxSmallpoxChickenpox1. Incubation P.: About 12 days (range : 7-17 days).About 15 days (range 7-21 days).2. Prodromal symptoms : Severe.Usually mild.3. Distribution of rash :* Palms and soles frequently involved* Axilla usually free* Rash predominant on extensor surfaces and bony prominences. Seldom affected Axilla affected Rash mostly on flexor surfaces.4. Characteristics of the rash* Deep-seated* Vesicles muitilocuiar and umbilicated* Only' one stage of rash may be seen at one time* Superficial* Unilocular: dew-drop like appearance* Rash pleomorphic, i.e., different stage of the rash evident at one given time, because rash appears in successive crops* No area of inflammation is seen around the vesicles* An area of inflammation is seen around the vesicles.5. Evolution of rash : * Evolution of rash is slow, deliberate and majestic, passing through definite stages of macule, papule, vesicle and pustule.* Evolution of rash very rapid* Scabs begin to from 10-14 days after the rash appears* Scabs begin to form 4-7 days after the rash appears6. Fever:* Fever subsides with the appearance of rash, but may rise again in the pustular stage (secondary rise of fever)* Temperature rises with each fresh crop of rash.It is a highly contagious disease. A centripetal pleomorphic rash appearing on the first day of the illness and has a relatively short course of illness.Children with chicken pox are removed from school or day care centres for 6 days after appearance of the rash.Varicella zoster immune gammaglobulin (VZ1G), 12S U/kg may prevent illness in household contacts if administered IM within 96 hrs of exposure particularly in:* Infants under 1 month of age* Prgnant with leukaemia* Patients on steroid therapy