The epidemiology of Herpes zoster in an urban population

A community-based case-control study was carried out in South London, to investigate the determinants of herpes zoster in adults without underlying immunosuppression. Incident zoster cases were identified from general practices. Two controls were selected per case, matched by age, sex, and practice. Participants were interviewed to determine exogenous contacts with varicella and with children as proxies for varicella contacts; ethnicity, country of birth and age at varicella; micronutrient Intake and intake of fruit and vegetables; ultraviolet radiation (UVR) exposure in childhood and in the last year, and stressful events. Odds ratios were estimated using conditional logistic regression. Data from 244 cases and 485 controls were analysed. On multi variable analysis, contacts with children significantly protected against zoster - most heavily exposed individuals were at one fifth the risk ofunexposed individuals, and this appeared to be mediated by increased exposure to varicella cases. Childhood UVR exposure was associated with a strongly increased risk of zoster. Individuals eating fresh fruit less than once a week were at a six- fold risk of zoster compared to those with highest intakes, and individuals aged >60 years with a high combined micronutrient intake were protected against zoster. Individuals experiencing an incident stressful event in the last two months were at more than twice the risk of zoster, and stressful events in the last year were associated with increased risk amongst elderly individuals. The protective effect of Afro-Caribbean ethnicity was mostly explained by increased child contacts and high fresh fruit intake. This study identified new risk factors for zoster. Those factors that were restricted to older individuals may also be determinants of immunosenescence. The findings suggest that widespread varicella vaccination ,of children could lead to increased incidence of adult zoster by decreasing exogenous varicella exposures. Other implications for future research and for public health policy are discussed