Lack of Evidence for Seasonal Variation in Herpes Zoster: A Nine-Year Retrospective Cross-Sectional Study

Herpes zoster results from the reactivation of latent varicella-zoster virus and may cause serious complications. Although traditionally considered nonseasonal, recent studies have reported summer peaks in herpes zoster occurrence. Given these inconsistencies, monthly and seasonal variations in herpes zoster case rates and their implications for prevention were evaluated in this study. In this retrospective cross-sectional study, the medical records of patients diagnosed with herpes zoster at a dermatology outpatient clinic between January 2017 and December 2025 were reviewed. Data on age, sex, and the year, month, and season of diagnosis were collected and analyzed using IBM SPSS Statistics for Windows, version 30.0. The highest proportion of herpes zoster cases occurred in patients aged 60–69 years. Visit-adjusted case rates did not differ significantly across months or seasons. A significant increasing trend in herpes zoster case rates was observed from 2020 to 2025. Herpes zoster is a vaccine-preventable disease that may cause serious complications and shows an increasing trend in occurrence. No statistically significant seasonal variation in herpes zoster occurrence was detected in this cohort, supporting the importance of maintaining year-round preventive strategies, including vaccination.