Herpes zoster and postherpetic neuralgia.

Herpes zoster (HZ; shingles) results from reactivation of varicella-zoster virus that has been dormant in the spinal and cranial sensory ganglia following primary infection with varicella (chickenpox), usually during childhood. In developed countries more than 95% of the adult population are seropositive for varicella-zoster virus and are therefore at risk of developing HZ. Reactivation can occur at any age, but it is associated with an age-related decline in cell-mediated immunity and therefore occurs more frequently in older adults. Thus, HZ affects up to 25% of individuals during their lifetime, but approximately 50% of those aged 80 years or more. Whilst the disease is rarely life-threatening, it is associated with a number of acute symptoms such as a vesicular rash and pain. Longer-term complications include visual disturbances and postherpetic neuralgia (PHN), which is potentially the most troubling problem of all, and is associated with severe itching and allodynia. These can combine to negatively impact the day-to-day functioning and quality of life of the patient. Hospitalization associated with HZ and PHN is frequent in older individuals and a significant cost to healthcare providers. Current management of HZ with antiviral drugs and analgesics produces reasonable results in younger patients, in whom the disease is usually milder, and is effective against acute pain and skin rash. However, it is much less effective against PHN, which occurs more commonly and more severely in older patients. Once PHN has developed, current treatments offer only limited benefit and adverse effects are common. Management is challenging and often unsatisfactory (<50% of patients gain 50% relief of pain). With the older adult population steadily growing in size, the number of patients presenting with HZ is also likely to increase and this will place a greater burden on healthcare systems. Prevention strategies, such as vaccinating those at greatest risk, may offer the best option for the future.