According to several studies, the onset of HIV-1 infection with the spread of CCR5-tropic viruses in the body is characteristic of HIV-1 subtype A as well as most virus genetic variants except for subtype D. Different studies on the use of CCR5 or CXCR4 coreceptors by HIV-1 belonging to non-B subtypes (including subtype A) involving naïve HIV+ patients demonstrate that the abundance of CXCR4-tropic viruses varies from 2 to 40%. The gene discussed is CXCR4; the disease is HIV-1 infection.