Raising the standard of evidence for determining modes of HIV transmission

Jafa and colleagues (1)⁠ report one of the strongest investigations of HIV transmission modes in adults yet. Their work substantially lifts the evidentiary bar for identifying modes of HIV transmission. Particular strengths of their investigation include focus on incident infection, multiple modes of transmission, time and place of exposures, contact tracing, network representation, and DNA sequencing HIV variants in infected persons.

Despite these considerable strengths, there are several important gaps in their investigation. We are puzzled that full data on the networks of sex, injection, and tattooing contacts were neither detailed nor related to variation in cases' HIV DNA sequences. Also, insights about transmission routes were significantly limited because the contacts (sexual, injection, and tattooing) of HIV seroconverters who reported sex while in prison were not elicited and traced. In addition, it is unclear what types of contact were included in the measured sexual exposures (anal, oral, and/or manual?), drug injection exposures (e.g., shared needles/syringes, other shared injection paraphernalia, syringe-mediated drug sharing, administering injections to others, receiving injections from others, and/or injecting together?), and tattooing exposures (e.g., shared implements, shared ink, receiving a tattoo from another, giving a tattoo to another, and/or tattooed at same time/place as another?). Depending on the scope of the measured exposures, associations with HIV infection may have been underestimated. Furthermore, it is concerning that other blood exposures in prison (e.g., from fights, piercing, shared razors, etc.) and the contacts involved in such exposures were not assessed.

Some of Jafa and colleagues' interpretations of their results do not correspond with the actual evidence reported. The authors minimize the potential importance of tattooing in the spread of HIV because “there is no documented case of HIV transmission via tattooing to date.” Not only does the evidence they present suggest a significant role for tattooing, but the positive association between tattooing (particularly in prison settings) and HIV infection is very well-established (2-19)⁠, and tattooing in prisons is especially unhygienic (20-22)⁠. In most prior studies, the relationship between tattooing and HIV infection was independent of other blood and sexual exposures. Curiously, the authors also attribute HIV infections to sexual exposures when cases had both sexual and blood (illicit drug injection and/or tattooing) exposures. Instead, the authors' data suggest that both sexual and blood (tattooing and drug injection) exposures were involved in HIV transmission, with the relative importance of specific modes unable to be distilled with the research design implemented.

To determine HIV transmission modes with confidence, it is necessary to assess blood and sexual exposures comprehensively for incident cases and controls, trace their corresponding contacts, and sequence infected persons’ HIV isolates (23; 24)⁠. Investigations that build on the authors' trailblazing work and employ the full research design we describe are sorely needed in other populations and settings, such as African-American women (25)⁠ and throughout sub-Saharan Africa, Asia, and the Caribbean. We can only hope that health ministries and HIV researchers everywhere will assign high priority to such fundamental investigations.

Devon D. Brewer, Interdisciplinary Scientific Research
John J. Potterat, independent consultant, Colorado Springs
Stephen Q. Muth, Quintus-ential Solutions
Stuart Brody, University of the West of Scotland

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No competing interests declared.