Human hepatitis B virus is the prototype for a family of viruses, referred to as hepadnaviridae. It has at least 4 subtypes, ayw, adr, ayr, and adw, among which subtype adr is the most prevailing in China.

• 人类乙型肝炎病毒属嗜肝DNA病毒科，至少有4种亚型：ayw、adr、ayr、和adw。