From November 2014 to May 2017, our team conducted multi-wave data collection with 346 current PWID in the rural interior of Puerto Rico via project supported by NIH grant R01DA037117. This research was organized around four specific aims: 1) Use network-based sampling, ethnographic fieldwork, and HIV and HCV testing to determine behavioral and structural factors affecting HIV and HCV incidence and prevalence rates among people who inject drugs (PWID) in rural areas of Puerto Rico; 2) Estimate the range of HIV and HCV prevalence and incidence rates in rural Puerto Rico for 5, 10, and 20 year time spans using network-structured, agent based simulation; 3) Simulate common interventions aimed at preventing HIV and HCV infection in a dynamic risk network environment to determine which interventions (or combinations of interventions) are most appropriate for preventing the spread of HIV and HCV among PWID in rural Puerto Rico; 4) In collaboration with our Dissemination Advisory Board, apply an integrated knowledge-exchange approach with our target audiences (policymakers, public health officials, and harm reduction providers in Puerto Rico and in New York, where many rural injectors go when they become HIV+). In September 2017, hurricane Maria devastated Puerto Rico's infrastructure. The impact of the disaster on drug-related morbidity and mortality are likely to be large. Currently, little is known about post-disaster patterns of drug-related risk of infection or overdose, outside of recent research under economic restructuring. What evidence exists points to an escalation of risk across the full range of HIV and hepatitis C infection scenarios. While the damage from Maria is relatively unprecedented, large scale natural and social disasters are increasingly common. From a planning and intervention perspective, greater understanding of the impacts of such events on (short term) overdose rates and (long-term) HIV/HCV infection prevalence are critical. This competing revision allows for an originally unanticipated wave of post-disaster data collection with rural PWID in Puerto Rico that will repeat strategies used to establish PWID risk network topologies and epidemiological dynamics during two waves of data collection in 2016 and 2017. Post-hurricane data collection will provide greater understanding of the impact of large scale social and ecological destruction on the range of factors associated with Aims 1-3. It will also allow our team to re-establish the integrated knowledge exchange with our Dissemination Advisory Board, whose understanding of the situation on the ground in Puerto Rico is likely to have shifted dramatically. While our specific aims remain the same, the impact of the overall project will be significantly expanded by the inclusion of a first-ever pre-/post-disaster network data collection among PWID.