Superinfection detected in up to 7% of people in Swiss HIV Cohort Study

Simon Collins, HIV i-Base

Researchers from the Swiss HIV Cohort Study have reported that evidence of HIV reinfection – sometimes called superinfection – was found in a longitudinal study in up to 7% of people living with HIV. [1]

The group developed a molecular epidemiology screening, using over 22,000 samples of HIV sequences from 4575 participants, and identified 325 potential cases of reinfection.

Of these, 128/325  were tested by near-full-length viral genome sequencing of biobanked plasma samples: 52/128 were confirmed, 15 were not confirmed, and 61 did not include the relevant time points for further evaluation.

HIV superinfection is generally only reported when drug resistance of the reinfecting strain causes viral rebound in someone who was previously undetectable and who has good adherence. Such cases have been reported for over 20 years, complicating clinical management due to reduced treatment options. [2]

This highly complex area of research is complicated by the difficulty of distinguishing reinfection from initial coinfections and needing new infections to outcompete the initial infection during the sampling window period. Taken together, reinfection is likely to be underestimated in all studies.

Other than when drug resistance is involved, multiple HIV infections has not been linked to poorer clinical outcomes, although this still hasn’t been formally studied in prospective longitudinal studies.

This is important. Poorer clinical outcomes have also not been reported for people who were initially infected with multiple compared to a single founder virus,


This study shows that HIV reinfection is common and likely underestimated.

However, reinfection itself has not be linked to poorer clinical outcomes, unless the second infection is with a drug-resistant strain.

This broader context of this theoretical risk depends on the setting. For example, whether both partners are using ART and are already likely to have a similar resistance profile, and, when this information is unknown, in the background population levels of drug resistance.


  1. Chaudron SE et al. A systematic molecular epidemiology screen reveals numerous HIV-1 superinfections in the Swiss HIV Cohort Study. Journal of Infectious Diseases, 226(7); 1256–1266. doi: 10.1093/infdis/jiac166. (1 October 2022).
  2. Collins S. HIV coinfection, reinfection and superinfection. HTB (1 September 2003).

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