Network structural dynamics acid infectious disease propagation

We aimed to relate dynamic changes in risk-network (sex and/or injecting dr ug) structure to observe STD/HIV transmission. We analysed macro-and micro- structural elements in 2 heterosexual networks, augmented by ethnographic o bservations. In a Colorado cohort of injecting drug users (n=595), measures of subgroup formation and of density of activity show decrease of network cohesion over time; only one HIV transmission was observed in 3 years. In a group of adolescent heterosexuals in Georgia (n=99), re reverse process (i ncrease in structural cohesion) was associated with efficient syphilis tran smission: TO cases were observed. Changes in personal risk behaviours over time were modest. STD/HIV transmission patterns were associated with intensification or dimin ution of network cohesion. Network and ethnographic data suggest that enhan ced connectivity facilitates transmission while segmentation impedes it, su ggesting opportunities for interventions. These data also emphasize the nee d to re-evaluate purely behavioural explanations of STD/HIV transmission.