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Varicella-zoster virus (VZV) is a herpes virus. Primary infection with VZV causes chickenpox and is predominantly a childhood disease. However, after infection, the virus persists in a latent state within the host in the nerves (i.e. dorsal root ganglia). Reactivation can occur years later, especially in immunosuppressed individuals, to cause shingles (herpes zoster).

The local manifestation of herpes zoster or shingles appears as vesicles with an erythematous base, sometimes in crops, irregularly on the skin in areas supplied by the sensory nerves of a single or associated group of dorsal root ganglia. Localised and disseminated shingles can occur with increased frequency in cancer patients and those undergoing immunosuppression therapy.

The infection is spread from person to person via the respiratory (airborne and droplet) route, by direct contact with the secretion of skin vesicles and indirectly through items freshly soiled by discharges from vesicles and mucous membranes of infected people. During this time, the patient is highly infectious and should be nursed in a negative pressure room with IPC precautions. When healing begins, the skin lesion vesicles become dry and form a scab. Crusted vesicles are no longer infectious. It must be noted, however, that contagiousness may be prolonged in individuals with suppressed immunity. Therefore, patients with VZV infection and susceptible (non-immune) persons exposed within the previous 21 days should not be admitted to the hospital unless necessary. Inpatients who develop varicella and susceptible patients (non-immune) exposed in hospital should be discharged as soon as possible if their clinical condition permits.

The disease is more severe in pregnant women, with a higher risk of fulminant varicella pneumonia. They should be isolated in a negative pressure side room with en suite facilities with IPC precautions.

It is important to remember that in the UK, seropositivity for VZV is about 90% of adults over the age of 18 years. Non-immune health workers exposed to VZV should be warned that they may develop chickenpox and should be reassigned to minimise patient contact for 8–21 days post-contact. Pregnant staff with no history of chickenpox must avoid contact with patients and colleagues with VZV infection. VZV vaccine should be offered to non-immune HCWs but is not recommended during pregnancy (refer to the Green Book for the most up-to-date guidance).

Passive immunisation with varicella-zoster immunoglobulin (VZIG) or antiviral prophylaxis with aciclovir may be indicated for exposed individuals who are non-immune to VZV and who are at high risk of severe infection or complications of infection. Refer to UK guidance on post-exposure prophylaxis for varicella or shingles for the most up-to-date guidance.