Superinfection identified in 2 out of 8 patients with unexpected viral load increases

Simon Collins, HIV i-Base

The rate and risk of reinfection with a second strain of HIV after primary infection are unclear with most instances reported as case studies. Reinfection clearly occurs, with viral load of the transmitting partner likely to be a significant risk factor. However, the clinical importance of a second infection, based on current limited data, appears largely related to acquisition of a resistant strain and its impact on reducing treatment options.

A pilot study by Doyle and colleagues at UCL looked for treatment-naive patients who were at risk of reinfection from sexual exposure, who experienced a significant viral load increase (>0.5 log) during routine viral load clinic monitoring. Eight patients were indentified (all sub-type B) and phylogenetic analyses were performed on the stored and most recent samples. In two patients, early sequences formed separate clusters to late sequences, with no evidence of viral recombination, indicating a second infection.

One patient was reinfected 5 months after his initial diagnosis during acute infection, and experienced similar seroconversion symptoms at the time of viral load increase. He also acquired syphilis and herpes in the subsequent 6 months.

A second patient had been diagnosed HIV positive 3 years earlier and experienced no symptoms and no other STIs at the time of superinfection. He controlled both the first infection and the superinfection without HAART, with a viral load set-point of 3.5 log10 copies/mL and a stable CD4 count >1000 cells/mm3.

These two cases indicate that reinfection is unlikely to be a rare event and can occur both in the early and established disease, even in the presence of effective immune responses.


While the study conclusion is that targeted screening based upon sexual history and viral load can achieve a high detection rate and is important in the context of transmitted resistance, it is not appropriate to conclude that early HAART should be used as a public health measure between consenting HIV-positive adults who choose to use neither condoms nor treatment.


Doyle T et al. High-risk sexual behaviour and HIV-1 superinfection: an indication for early initiation of antiretroviral therapy? 15th Annual Conference of the British HIV Association (BHIVA), 1-3 April 2009, Liverpool. Poster abstract P150.

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