Estimates for the contribution of transmission arising from acute HIV infections (AHI) to overall HIV incidence vary significantly. Furthermore, little is known about AHI-attributable transmission among people who inject drugs (PWID), including the extent to which interventions targeting chronic infections (e.g., highly active antiretroviral therapy [HAART] as prevention) are limited by AHI transmission. Thus, we estimated the proportion of transmission events attributable to AHI within the mature HIV epidemic among PWID in New York City (NYC).
We constructed an interactive sexual and injecting transmission network using an agent-based model simulating the HIV epidemic in NYC between 1996-2012. Using stochastic microsimulations, we catalogued transmission from PWID based on the disease stage of index agents to determine the proportion of infections transmitted during AHI (in primary analyses, assumed to last three months).
Our calibrated model approximated the epidemiological features of the mature HIV epidemic in NYC between 1996-2012. Annual HIV incidence among PWID dropped from approximately 1.8% in 1996 to 0.7% in 2012. Over the sixteen-year period, AHI accounted for 4.9% (10/90 percentiles: 0.1%-12.3%) of incident HIV cases among PWID. The annualized contribution of AHI increased over this period from 3.6% in 1996 to 5.9% in 2012.
Our results suggest that, in mature epidemics such as NYC, between 3-6% of transmission events are attributable to acute HIV infection among people who inject drugs. Current HIV treatment as prevention strategies are unlikely to be substantially affected by AHI-attributable transmission among PWID populations in mature epidemic settings.