Herpes zoster infection

### What you need to know Herpes zoster is caused by reactivation of a primary infection with varicella zoster virus.1 After a primary infection, the virus lies dormant in dorsal root or cranial nerve ganglia. Reactivation causes the typical dermatomal pain and vesicular rash (fig 1). Fig 1 Vesicular rash caused by herpes zoster Varicella zoster (commonly known as chickenpox) and herpes zoster (commonly known as shingles) are caused by the same herpes virus. Varicella follows the initial infection and causes a generalised rash, whereas herpes zoster occurs after reactivation, years later, and symptoms are usually localised to a specific dermatome. The overall annual incidence of herpes zoster in the UK is estimated to be 1.85-3.9 cases per 1000 population,2 increasing with age from fewer than two cases per 1000 among people under 50 to 11 cases per 1000 among people aged 80 or older. In the US, incidence ranges from 1.2 to 3.4 cases per 1000 person years, increasing with age to 3.9 to 11.8 cases per 1000 person years among people aged 65 or older.34 ### Who is at risk? Over 90% of adults in the US have serological evidence of primary varicella …