When Both Partners are Infected:

When Both Partners are Infected: What is the Significance of Superinfection in HIV Transmission?

Superinfection is defined as infection by a second strain of HIV after initial infection by a primary strain has been established [44]. The frequency and timing of superinfection may vary depending upon the population under study and the method of detection. Follow-up of 78 newly infected individuals (none of whom initiated ART while under study) in one clinic revealed that 4 (5%) had acquired a superinfecting strain within 6 to 12 months of initial infection [45]. In a cohort of 36 high-risk Kenyan women screened for HIV-1 superinfection over a 5-year period beginning at primary infection, seven cases of superinfection were detected [46]. In this study superinfection occurred throughout the course of the first infection: during acute infection in two cases, between 1-2 years after infection in three cases, and as late as 5 years after infection in two cases. The clinical consequences of superinfection for an individual vary, but may include accelerated disease progression and the acquisition of drug resistance [47]. The public health consequences of HIV superinfections are unclear. While superinfection can result in recombination between genetically different viruses, and a number of circulating recombinant forms (CRFs) are prevalent in certain geographic areas [48], it has not been demonstrated that such recombination results in the establishment of more transmissible or virulent viruses. There is also evidence that superinfection occurs only rarely in HIV-infected individuals on effective ART [49, 50] .