- Primary varicella infection (chickenpox) and herpes zoster (shingles) are both caused by varicella zoster virus (VZV).
- Primary varicella infection is generally a mild and self-limiting condition in children, but has a higher rate of complications in adolescents and adults as well as immunocompromised patients, pregnant women and neonates. Varicella pneumonia, encephalitis, and hepatitis are significant sources of morbidity and mortality.
- Herpes zoster represents reactivation of varicella zoster virus from cranial nerve or dorsal root ganglia, thus affecting the skin in a dermatomal distribution. It can disseminate to both the skin and internal organs, most commonly the central nervous system.
- The hallmark lesion of primary varicella and herpes zoster is a vesicle or pustule on an erythematous base. In zoster, multiple lesions are grouped and/or present within a dermatomal distribution.
- A common complication of herpes zoster is post-herpetic neuralgia (PHN), the development of persistent pain and/or dysesthesia at the sites previously affected by herpes zoster. There is limited evidence to support a definitive intervention to prevent the development of PHN. Management of PHN includes nerve-directed therapies.
- Primary varicella infection and disseminated zoster can be a dermatologic emergency in patients who are immunocompromised and in pregnant women.
Varicella zoster virus (VZV) is a human herpesvirus (HHV3) that causes both primary varicella infection and herpes zoster. Primary varicella is highly contagious, and prior to the introduction of varicella vaccination, the lifetime prevalence of primary varicella was approximately 90%, with most cases occurring during childhood. This virus is spread through respiratory and salivary secretions during periods of viremia and results in nonspecific symptoms (fever, headache, malaise) followed by a generalized pruritic vesiculopustular eruption. Since the introduction of childhood varicella vaccination, the rates of primary varicella infection have been dramatically reduced. Typically, primary varicella infection is self-limited and requires only symptomatic treatment. However, infection of adults may be severely debilitating, requiring systemic antiviral medication and possibly hospitalization. The most common extracutaneous site of involvement is the lungs (varicella pneumonia), though it may also cause encephalitis or hepatitis, as well as other less common internal manifestations. Secondary bacterial infection of lesions is another source of significant morbidity. Primary varicella infection of pregnant women may result in intrauterine infection (especially in the first or second trimesters of pregnancy), resulting in congenital varicella syndrome, a syndrome marked by significant morbidity and mortality to both mother and child.
Herpes zoster represents the reactivation of VZV from the cranial nerve or dorsal root ganglion with presentation of a painful vesicular rash in a dermatomal distribution. Prior to the development of the zoster vaccine, the lifetime incidence of zoster in the adult American population was 10-20% with increased risk with advancing age; the incidence of zoster approached 50% in individuals over the age of 85. Zoster vaccination, generally recommended for individuals over the age of 60, significantly reduces the risk of zoster reactivation as well as hospitalization for zoster and post-herpetic neuralgia. The zoster vaccine, like that for varicella, is made from live attenuated virus and is therefore contraindicated in immunocompromised patients.
Herpes zoster can undergo cutaneous dissemination, defined as the presence of greater than 20 skin lesions outside of the primary and immediately adjacent dermatomes (though occasionally it can present with diffuse generalized lesions from the outset, as with primary varicella). Cutaneous dissemination is important because it is associated with a higher risk of visceral dissemination, most commonly to the central nervous system. Central nervous system zoster can present with cranial nerve palsies, encephalitis, meningitis, and stroke (the latter of which is becoming an increasingly recognized sequela of herpes zoster). Immunocompromised and immunosuppressed individuals are at higher risk for disseminated zoster. Cases of disseminated zoster with visceral involvement (central nervous system, lungs, liver or GI tract) may be fatal. Patients with cranial nerve V1 involvement require ophthalmologic evaluation to rule out the possibility of ocular disease, including retinitis and acute retinal necrosis.
In localized (single dermatome involvement) herpes zoster, treatment with systemic antivirals is the standard of care, especially in patients presenting with early lesions; early intervention with systemic antivirals may shorten the course of disease. Patients are considered infectious through respiratory secretions, saliva and direct viral shedding from skin lesions until these lesions crust over. It is thus recommended to keep the lesions covered if possible and to avoid contact with immunocompromised patients, pregnant women, and patients who have never had varicella or been vaccinated. The rate of transmission goes up significantly if the patient is immunocompromised or has disseminated disease, necessitating both contact and airborne isolation precautions in the inpatient setting.
Although there is excellent data suggesting that systemic antivirals reduce the duration of zoster lesions, reduce associated pain, and reduce viral shedding, there is limited evidence to support a definitive intervention to prevent the development of post-herpetic neuralgia (PHN), other than zoster vaccination. PHN is the development of persistent pain and/or dysesthesia at the sites previously affected by herpes zoster, lasting beyond 3 months after the initial infection. In one study, the incidence of PHN (defined by pain within the previous 12 months at the site affected by herpes zoster) at 9 years following herpes zoster was 21%, and risk factors associated with the development of PHN included pain preceding the development of cutaneous rash by >72 hours and moderate to severe pain with rash, increased severity of rash, and female gender. Elderly patients are also more likely to develop PHN.