This paper identifies an important paradigm shift in social research on HIV transmission, drug abuse, and risk reduction research. The article describes the key research trends and the institutional support for social network analysis in the HIV and drug risk field for the past decade. Key hypotheses and recommended areas for future research are identified.

The research below is about modelling complex social systems, and in particular applications of Cellular Automata. This is a collaboration of variety of initiatives such as MoCSSy, CSMG, IMPACT-HIV at the IRMACS centre in Simon Fraser University and the BC Centre for Excellence in HIV/AIDS. This project was supported by the MITACS NCE of Canada and Maplesoft. 1 IDU, HIV, social influence, transmission dynamics, herd immunity Injection drug users (IDU) who share needles are at high risk for contracting human immunodeficiency virus (HIV) infection. Social and behavioral influences that promote needle sharing can, therefore, impact HIV transmission. HIV spreads rapidly in IDU communities and interventions that target needle-sharing have had variable results. We constructed a cellular automaton model to study the dynamics of the HIV epidemic in an IDU community, in the presence of influences that promote or discourage sharing of used needles. Peer influences are tracked by a counter associated with each individual, who begin or stop sharing needles once a threshold level of influences from neighbours is

Scrapie is a small ruminant, transmissible spongiform encephalopathy (TSE). Although in the past scrapie has not been considered a zoonosis, the emergence of bovine spongiform encephalopathy, transmissible to humans and experimentally to sheep, indicates that risk exists for small ruminant TSEs in humans. To identify the risk factors for introducing scrapie into sheep flocks, a case-control study was conducted in France from 1999 to 2000. Ninety-four case and 350 control flocks were matched by location and main breed. Three main hypotheses were tested: direct contact between flocks, indirect environmental contact, and foodborne risk. Statistical analysis was performed by using adjusted generalized linear models with the complementary log-log link function, considering flock size as an offset. A notable effect of using proprietary concentrates and milk replacers was observed. The risk was heterogeneous among feed factories. Contacts between flocks were not shown to be a risk factor. Scrapie is a transmissible spongiform encephalopathy (TSE) affecting sheep and goats (1), as is Creutzfeldt-Jakob disease (CJD) in humans or bovine spongiform encephalopathy (BSE) in cattle. Moreover, scrapie is contagious in natural conditions (2). Though genetic determinism is a major feature of scrapie, the infectious agent is nonetheless needed for the disease to develop (3,4). Known to exist for centuries, scrapie was thought to be a possible origin of BSE, although this hypothesis has not yet been verified. Sheep and goats can be experimentally infected with BSE, resulting in a disease that is impossible to distinguish from natural scrapie (5). Since BSE is implicated in the emergence of variant CJD (6,7), the existence of BSE in small ruminants poses a further risk for human health. Scrapie has become a public health challenge, and its propagation must be stopped; therefore, the risk factors for the introduction of scrapie in sheep must be understood. In sheep infected with scrapie, the infectious agent is widely distributed in the organism. In particular, the