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Shingles (herpes zoster) is caused by the reactivation of a latent varicella zoster virus (VZV) infection, sometimes decades after the primary infection.
Primary VZV infection typically occurs during childhood and causes chickenpox (varicella). Following primary VZV infection, the virus enters the sensory nerves and travels along the nerve to the sensory dorsal root ganglia and establishes a permanent latent infection. It is not known what causes reactivation of the latent virus, which leads
to the clinical manifestations of shingles, but reactivation is usually associated with conditions that depress the immune system such as immunosuppressive therapy, HIV infection and/or old age.
The incidence of shingles in England and Wales is estimated to be around 790 to 880 cases per 100,000 people per year for those aged 70 to 79 years.
The risk and severity of shingles increases with age.