Increasing incidence of varicella-zoster virus meningitis in Japan, 2011-2022

The epidemiology of varicella-zoster virus (VZV) meningitis, including its optimal management, in Asia remains unclear. This study aimed to clarify the incidence, treatment patterns, and outcomes of VZV meningitis in Japan. We identified 1680 patients with VZV meningitis between April 2011 and March 2023 using the Diagnosis Procedure Combination (DPC), a national inpatient database in Japan. The annual incidence of VZV meningitis was calculated as the number of patients with VZV meningitis divided by the annual population, and adjusted for the proportion of acute-care hospitals covered by the DPC. We described the eligible patients' treatment regimens (including antiviral agents) and clinical outcomes (in-hospital mortality and Barthel Index at discharge). The average annual incidence was 0.25 per 100,000 person-years, increasing from 0.13 in 2011 to 0.46 in 2022. Overall, 96.4% of patients initially received high-dose intravenous acyclovir therapy with a median duration of 11 days. Of the patients treated with intravenous acyclovir, 89.3% received long-course treatment (≥7 days). The in-hospital mortality was 0.8%, and the Barthel Index at discharge was ≥90 in 87.4% of patients. The incidence of VZV meningitis has more than tripled in Japan in the last 12 years. Most patients were treated with long-course intravenous acyclovir and had favorable outcomes at discharge.