The risk of becoming superinfected (contracting another strain of HIV to the one you have already) may be as high in the community as the risk of contracting HIV, according to a paper released in February 2012.
Superinfection can be difficult to detect, claim the writers, and is undoubtedly underdiagnosed.
However, many superinfections are unlikely to be clinically relevant.
Studies show wide variations in the incidence of superinfection, from no detected cases to rates close to those of HIV infections in the background population. This is due to wide variation in several factors including laboratory methods, sample timing and frequency, HIV-1 subtype, ongoing risk behaviour and ART use.
Seroconcordant partners with no differences in HIV resistance pattern can rest assured, the writers advise, unless one individual develops new, significant resistance. Those with an unexpected, unexplained jump in viral load levels should undergo repeat resistance testing if they are at risk of superinfection.