Current Status of Hepatitis B Virus Genotypes in Carriers in Western Shikoku, Japan

This study investigated the distribution of hepatitis B virus (HBV) genotypes in western Shikoku, Japan, particularly focusing on genotype D. We retrospectively analyzed 707 HBsAg-positive patients who underwent HBV genotyping from 2011 to 2024. Patients were stratified by age: < 40, 40-49, 50-59, and ≥60 years. Genotype D was observed in 20%-30% of patients aged 40-59 years, but only 3.7% in those aged < 40 years, demonstrating the influence of perinatal transmission prevention and public health initiatives. Conversely, 1.6%-7.0% of younger generations had genotype A, raising concerns owing to its higher risk of chronicity following horizontal infection. These findings suggest that although the prevalence of genotype D infections has significantly declined, ongoing surveillance and awareness campaigns remain essential for controlling genotype A transmission.