VZV

Primary varicella is spread by respiratory droplets and airborne route and produces fever with a generalized, intensely pruritic vesicular rash in which lesions appear in successive crops, so macules, papules, vesicles, and crusts are present simultaneously; the rash is centripetal, denser on the trunk than the limbs. Complications include secondary bacterial superinfection with Staphylococcus aureus or Streptococcus pyogenes, varicella pneumonia (much more severe in adults and pregnancy), cerebellar ataxia, and Reye syndrome if aspirin is given. The virus then travels retrograde along sensory axons to ganglia, where it lies latent. Reactivation, favoured by age and immunosuppression, produces herpes zoster: a painful dermatomal vesicular eruption that respects the midline. Ophthalmic zoster with vesicles on the nose tip (Hutchinson sign) threatens the eye, and Ramsay Hunt syndrome involves the geniculate ganglion with facial palsy and ear vesicles. Postherpetic neuralgia is the commonest sequela. Aciclovir, valaciclovir, and famciclovir are used; the recombinant zoster vaccine is preferred in adults over fifty.