One fifth of all cancers worldwide are caused by a chronic infection, for example human papillomavirus (HPV) causes cervical cancer and hepatitis B virus (HBV) causes liver cancer.

• 全世界有五分之一的癌症是由慢性感染引起的，例如人类乳头瘤病毒引起宫颈癌和乙肝病毒引起肝癌。