An ethno-epidemiological model for the study of trends in illicit drug use: Reflections on the 'emergence' of crack injection

Public health, including the prevention of drug use, has long relied upon sentinel marker data obtained from national and regional tracking systems in order to forecast changes in patterns of drug abuse. More recently, these types of data have also played an important role in monitoring particular types of medical consequences associated with drug use, including the spread of HIV, HBV, HCV and other viral infections prevalent in IDU populations. While these types of data may provide an important sources of information about changes in drug use and its consequences, the limits of these sources of data have also become widely apparent. Based on a patchwork of institutionally-derived sources of data (e.g. emergency departments, drug treatment admissions, and law enforcement data on drug seizures and arrests), sentinel marker data typically fail to capture a number of "hidden populations" evidencing "hidden" drug-related risk behaviours. Many of these populations and behavioural practices only become apparent well after they have become diffused across regions and diverse drug user subpopulations, making prevention more difficult and more expensive. Furthermore, these systems cannot capture patterns of episodic use, such as those evidenced in crack injection. Ethnographic methods, including field-based community assessment, semi-structured qualitative interviews, and targeted observation of "natural" venues in which drugs are bought, sold, and used, have the potential to overcome some of the limitations from which "systems data" often suffer. Drawing on an ethno-epidemiological approach, our ongoing multi-site research on the use of injection as a mode of administration in the use of crack cocaine is a case in point, and illustrates the potential utility an ethnographic model for the identification and tracking of emergent and ongoing drug use practices.