Degrees of Separation: Social & Spatial Networks of HIV & HCV

In 1929, Frigyes Karinthy posited a theory many of us might attribute to Kevin Bacon: everyone on the planet is but six degrees of separation (or less) from one another. Depending on how one would measure a connection, that metric is likely far less than it was in 1929. Beyond social media marketing, connecting these networks of friends and friend-of-friends has been pretty important to the concepts of “partner testing and notification” utilized by disease intervention specialists to disrupt chains of transmission in terms of STIs and HIV. What’s been less well understood is the geographic relationship between areas experiencing outbreaks or “clusters” or the specific venues in which transmission occurs – social-spatial networks.

A study performed in New Delhi sought to better understand the relationship between social circle and gathering venue among “hard to reach populations” homeless people and/or, particularly, people who inject drugs. Originating recruitment from within community, asking community to propel recruitment, and paying particular attention to the “mutuals” between otherwise unconnected participants, the researchers sought to better understand the relationship of “risk” of transmission not just in behavior or large geographic area but in specific places in which specific behaviors are part of the culture – the community standards, if you will - of that venue. Researchers found 65% of participants had HCV antibodies, of which 80% had an “active infection” and most were unaware of their HCV status. Similarly, of those participants living with HIV, 65% were directly connected with another participant living with HIV. Researchers did not specify these connections to be causative – those connected did not necessarily transmit either virus to one another. Further, researchers found partaking at the most popular venue was associated with a 50% greater likelihood of a participant having an HIV or HCV diagnosis. Even if a participant did not access the most popular venue, if they associated with someone who did, their likelihood for being diagnosed with HIV or HCV was 14% higher. And the more degrees of separation a participant had from someone who accessed the most popular venue, the less the likelihood of a diagnosis.

The researchers conducting the study were hoping to identify methods of understanding that would allow for effective interventions that reach beyond the individual level. Can group behavior be influenced beyond recruitment and toward changes? Can harm reduction strategies or housing programs find greater efficacy, a better stretch of our dollars, by better understanding where these networks exist and how they operate?

Or is this association merely a by-product of sharing certain characteristics society has deemed unworthy of care? Those social ills that drive disparities in health and poverty and addiction may also drive those experiencing these harms of bias and negligence to seek a social network that at least understand their struggles. To be a little less alone in these struggles.

As is the nature of most things, a better understanding of behavior doesn’t always lend itself to building positive interventions. The same ability to navigate networks in areas where people living with HIV are discriminated against and people who inject drugs can easily be criminalized, rather than connecting to care. With molecular surveillance generating the ire of HIV advocates over fear of this kind of detailed knowledge being used by law enforcement, advocates should also keep a keen eye on how networks may be weaponized as well.

Understanding the spatial relationship within a social network could be a powerful public health tool that shifts our focus from individual intervention to far more meaningful interventions, so long as we can keep the focus of this type of research and the information gathered from it squarely aimed at building up the “public” part of public health rather the continuing to push the responsibility of public health on individual behavior.