Shingles or herpes zoster is caused by reactivation of the varicella zoster virus, generally many years after the initial infection.1
Primary infection with the varicella zoster virus causes chickenpox, and usually occurs in childhood. After the primary infection, there is a permanent asymptomatic latent infection. The virus resides in the sensory cranial nerves and the sensory dorsal root ganglia.1
The virus can become re-activated, especially in immunosuppressed individuals, for example, those taking immunosuppressive medication or with HIV. Increasing age is a risk factor for varicella zoster reactivation, and this may be related to a decline in cell-mediated immunity. Furthermore, increasing age is associated with a more severe clinical manifestation of shingles.2
Shingles is common, affecting one in four individuals at some point in their lifetime.2 The annual incidence of shingles in England and Wales is estimated to be 880 cases per 100,000 people among those aged 70-79 years.3
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