Despite the fact that subtype C appeared in southern Brazil more recently than subtype B, it is now the predominant strain in Rio Grande. The epidemic spread of subtype C could be taking place in Brazil, and possibly in south America, a phenomenon similar to that seen in other countries where this subtype is now totally dominant.

Prospective studies that include detailed measurements of correlated sexual risk behaviors are required to discern whether this association is causal in nature; if so, these behaviors could represent an important area for future HIV prevention interventions.