1. Department of Gastroenterology, Kanazawa University Hospital, Ishikawa, Japan.
2. WHO Collaborating Center for Viral Hepatitis and Liver Cancer in WPRO, Kanazawa, Ishikawa, Japan.
3. Department of Epidemiology, Infectious Disease Control and Prevention, Graduate School of Biomedical and Health Sciences, Hiroshima University, Hiroshima City, Hiroshima, Japan.