General Virology and DNA Viruses
True about varicella is following except:
|A||One stage of rash is seen at on time.|
|B||Humans are the only known reservoir.|
|C||Children between 5–10 years old are most comm. -only affected.|
|D||Patients are infectious ~48 h before onset of the vesicular rash and until all vesicles are crusted.|
One stage of rash is seen at one time.
a. The skin lesions of chickenpox VZV —the hallmark of the infection—include maculopapules, vesicles, and scabs in various stages of evolution.
b. These lesions, which evolve from maculopapules to vesicles over hours to days, appear on the trunk and face and rapidly spread to involve other areas of the body.
c. Most are small and have an erythematous base with a di- ameter of 5–10 mm. Successive crops appear over a 2- to 4-day period. Lesions can also be found on the mucosa of the pharynx and/or the vagina.
a. Is an acute highly infectious disease caused by Varicella zoster virus.
b. As a rule, infectious diseases are not communicable during the incubation period, except, measles, chicken pox, whooping cough and hepatitis A, which are common during the later part of Incubation Period.
c. A painful, vesicular, pustular “dew-drops” like pleomorphic centripetal rash/eruptions in the distribution of one or more sensory nerve roots is characteristic feature (palms and soles usually not affected).
d. The virus can be readily isolated from the vesicular fluid during the first three days of illness.
e. Scabs begin to form 4-7 days after rash appears.
f. The scabs are not infective.
g. The secondary attack rate in household contacts approaches 90%.
h. It is transmitted from person to person by droplet infection and nuclei, and most patients are infected by “face to face” contacts.
i. IP = 14-16 days.
j. Infectivity of chicken pox and hence the duration of isolation for Chicken pox is until all lesions crusted: usually about 6 days after onset of rash from the onset of catarrhal stage412.