A model of HIV transmission by syringe sharing in English prisons using surveys of injecting drug users.

Important note: Information in this article was accurate in 1992. The state of the art may have changed since the publication date.

A model of HIV transmission by syringe sharing in English prisons using surveys of injecting drug users.

Int Conf AIDS. 1992 Jul 19-24;8(1):Mo12 (abstract no. MoD 0038). Unique Identifier : AIDSLINE ICA8/92399993
Dolan K; Medley G; Stimson GV; Centre for Research on Drugs and Health Behaviour, University of; London, UK.

Abstract: OBJECTIVES: To construct a model of HIV transmission and the effects of prevention strategies by using survey data and HIV prevalence data for IDUs. METHOD: Assume: each IDU only has access to one syringe at a time and IDUs (n) using a syringe share it randomly. Probability of transfer of infection when an uninfected IDU uses the syringes after an infected IDU is (B). Mean time spent using a syringe (L) is constant. When an IDU leaves the next IDU (ie n is kept constant) has a probability (Q) of being infected. These assumptions give a reversible Markov chain model describing the probability that i/n IDUs are infected. Estimates for the four parameters are (central estimate followed by range): n = 9 (2, 25); B = 5% (1%, 15%); L = 30 wks (5, 50); Q = 10% (5%, 15%). Values are from survey data, but sensitivity analysis for parameters values were conducted. RESULTS: Model shows that reducing B, L and Q always reduces the equilibrium proportion of IDU infected. A nonlinear relationship with n, means most infections occur for intermediate values (up to 10). Resulting peaked curve is due to interaction between infection rates and leaving the syringe. Using above estimates, preliminary results suggest that 2% (range: 0.05% to 32%) of sharers in prison become infected per year. If 3,080 IDUs share syringes in prison per year then 62 (range: 2 to 986) IDUs become infected in prison annually. CONCLUSIONS: The number of HIV infections occurring in prisons is calculated. This could be decreased by reducing; 1) time IDUs spend sharing syringes; 2) the proportion of users infected and sharing syringe; 3) the probability of transmission. Infection may increase if number of people per syringe is reduced. To alter these parameters requires major policy changes. Collection of HIV prevalence and incidence data in prison is needed to validate model.

Keywords: Animal England/EPIDEMIOLOGY Equipment Contamination Human HIV Infections/EPIDEMIOLOGY/*TRANSMISSION Injections, Intravenous/*ADVERSE EFFECTS/INSTRUMENTATION Markov Chains *Models, Theoretical *Prisoners Substance Abuse, Intravenous/*COMPLICATIONS/EPIDEMIOLOGY ABSTRACT
921230
M92C5354

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