h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Why do some illnesses, like chicken pox, have a different (and nastier!) effect in adults than children? Why does the virus, or whatever, create a different set of symptoms for each?

Well I'm not in a position to be specific but infants have a significantly different physiology to adults due to simple differences such as body size and more subtle differences such as the levels of various hormones in the body. Adult's immune systems may be slower to respond to invasion that those of vigorous youths.

It's not always a case of being worse in childhood either - some are worse in childhood than in adulthood - although I expect you knew that.

I don't think the symptoms of chicken pox itself are actually all that different between children and adults to be fair. I think the extremely bad region of the spectrum of symptoms is more likely to occur in adults. The later manifestation shingles is a recurrence after many years of lying dormant in the body and so wouldn't occur in a child anyway.

Kids can have shingles. I saw a few cases during my Paediatrics rotation.

It depends more of the state of your immune system. When it weakens the dormant varicella zoster virus reativates and manifests as shingles.

Well maybe I should have said under normal circumstances

hey, don;t worry Orcus, not your fault you don;t know what 'normal' is

Thanks for the answers though, I guess I just hadn't thought of adult and child immune and body systems as that different, but of course they are.

Is it also to do with pre/post pubescent physiology? I'm thinking of mumps, for instance, where in an adult male, the testes may be affected with worse symtoms than in a child!

Absolutely

My Entry on Chickenpox and Shingles atA3022525 goes some way towards answering the original question - older people have weaker immune systems.

A3022525