Due to varicella zoster virus (VZV). Spreads by droplets from upper respiratory tract and from the discharge of ruptured lesions. Highly infectious/contagious – affects children < 10 years. Incubation of 10-14 days. More common during late winter and early spring. More severe if >13 yrs of age.
Mild fever and illness for 1 or 2 days before skin lesions; pruritic skin eruptions or blisters form scabs after 24 hours – more common on trunk then spread to extremities. New blisters appear every 2 - 3 days – last for 5-7 days. Lesion may be portal for secondary bacterial infection. Lesions are infectious until turned into dry crusts.
Usually a benign self limiting condition. Complications – lymphadenitis; Reye syndrome; pneumonia; encephalitis; transverse myelitis; optic neuritis; myocarditis; glomerulonephritis; secondary bacterial infections; necrotising fasciitis.
If intrauterine infection congenital limb defects
Herpes zoster – occurs later due to reactivation of VZV in a dorsal root ganglion vesicular rash in dermatomal distribution.
Cool compresses reduces the `itchiness' of the blisters and discourages scratching by the child; acyclovir; (salicylates/aspirin contraindicated due to association with Reye syndrome).