Herpes Zoster

Definition/diagnostic criteria Herpes Zoster, also known as shingles, is a painful skin rash caused by reactivation of the varicella-zoster virus (VZV), the same virus responsible for chickenpox. Herpes Zoster is characterised by a unilateral, painful rash, typically distributed in a dermatomal pattern. It’s diagnosed primarily on clinical grounds, with a history of pain and characteristic rash in a dermatomal distribution. Vesicles may appear in crops over three to five days and can become pustular or form crusts. Diagnosis is largely clinical but can be confirmed with PCR testing of vesicle fluid or antibodies testing for VZV.

Epidemiology Herpes Zoster is common and can affect individuals of any age but is more frequent and severe in older adults (>50 years) and those with weakened immune systems. Approximately 25% of the population will develop herpes zoster during their lifetime. Incidence increases significantly with age, starting from 50 years old and above.

Diagnosis

Clinical Features: Herpes Zoster typically presents with pain, tingling, or itching in a dermatomal distribution, followed by the appearance of clustered red vesicles. The rash usually affects a single dermatome and does not cross the midline. Commonly involved areas include the thoracic dermatomes, cranial nerve distributions (particularly the ophthalmic division of the trigeminal nerve), and lumbar and cervical regions.

Investigations: While the diagnosis is mostly clinical, swabbing of the vesicle fluid for polymerase chain reaction (PCR) testing is the most accurate test to confirm VZV infection. PCR can differentiate between wild-type and vaccine strains. Increased antibodies titres to VZV can also support the diagnosis but are more useful for epidemiological purposes than individual diagnosis.

Treatment The mainstay of treatment for herpes zoster is antiviral therapy, primarily including aciclovir, valaciclovir, or famciclovir. Early treatment (within 72 hours of rash onset) can reduce the severity and duration of pain and may reduce the incidence of postherpetic neuralgia (PHN).

Prescribe antivirals if there is immunocompromise, non-truncal involvement, moderate or severe pain, moderate or severe rash. Also, consider treating all those over the age of 50.

In higher risk patients, consider prescribing up to one week after rash onset.

Analgesics may also be necessary to manage pain.

Seek specialist advice for ophthalmic zoster.

Prevention A shingles vaccination programme was introduced in September 2013 in the UK.

Prognosis The acute symptoms of herpes zoster typically resolve within 2 to 4 weeks. However, complications can occur, the most common being postherpetic neuralgia (PHN), characterized by persistent pain at the site of the rash after the rash has resolved. The risk of PHN increases with age. Other complications may include secondary bacterial infection, motor neuropathy, meningitis, or disseminated disease, particularly in immunocompromised individuals.