Nationwide Retrospective Observational Study of Herpes Zoster Associated Hospital Admissions in Italy

Varicella (chickenpox) is a highly contagious illness sustained by an α Herpes virus called varicella-zoster virus (VZV). A replication phase in the penetration site is followed by a viremic phase when VZV spreads to skin and mucosae, leading to the typical rash and infection of sensory nerves in the epithelium, and then the reach of the sensory ganglia where it becomes latent. The reactivation of the latent virus, years or decades after primary infection, causes the typical clinical expression called Herpes Zoster (HZ) or shingles.

Post-herpetic neuralgia (PHN), an intractable pain in the dermatome affected by HZ, is the most common complication. It is estimated that it affects 10-20% of all patients with HZ aged ≥ 50 years and up to 30% of those aged ≥80 years. Management of PHN is not easy, but vaccination for prevention of PHN may be a strategic choice.

The most common complications of herpes zoster, other than PHN, often requiring hospitalization, include secondary bacterial infections, ophthalmic complications, cranial and peripheral nerve palsies, and segmental zoster paresis.

All authors agree that factors such as age, cell-mediated immunity (CMI) depression, intrauterine exposure to VZV and varicella occurring in early age (<18 months) are typically associated with HZ incidence. It further should be noted that age and CMI depression are strictly related since increasing age leads to CMI decrease. An increased incidence of hospitalization for HZ among patients aged >72 years (0.46/1000-person year), compared to those aged 15-44 years (0.03/1000-person year) was reported, suggesting that aging is also a risk factor for HZ requiring hospitalization. Besides age, HZ risk can be related to other co-morbidities, including diabetes, major depression or immunosuppressive therapies, that induce reduced VZV-specific CMI response. Immunosuppressed patients are within the high-risk group, with increasing morbidity and mortality associated with herpes zoster. Immunosuppression may be associated with malignancy (especially hematological), human immunodeficiency virus (HIV) infection or medications used for organ transplantation or autoimmune disease.

HZ incidence is similar all over the world and its trend is related to population age, with two thirds of the cases affecting subjects aged >50 years.