 Additionally, the tendency of HIV-1 virions to recombine when two subtypes infect a single cell increases its susceptibility to HIV superinfection.Further evidence of superinfection stems from the fact that nearly 10% of HIV-1 infections are associated with a transmittable recombinant strain.HIV-1 virions are divided into nine subtypes, all of which are characterized by different rates of disease progression, viral load and sensitivity to assays used in detection.