CCR5 and infection: At present, sexual transmission is the primary mode of transmission in China and CRF01_AE has become the predominant subtype in Chinese HIV-1 sexually infected patients [21], the high CXCR4-use in CRF01_AE may lead to reduced susceptibility to CCR5 antagonists, which emphasise the need for viral tropism screening in CRF01_AE infections in China.