Background: To characterize the temporal trends from 1987 to 2001 and cofactors of the prevalence of HIV and HCV infections among 2,219 injecting drug users (IDU) starting substance abuse treatment in two large hospitals in metropolitan Barcelona.

Methods: IDU with HIV tests done from 1987 to 2001 and admitted for heroin detoxification comprised the study population. Testing for HCV started in 1991 (n= 1,132). Cofactors of interest included: sex, duration of IDU, age and year of initiation and history of imprisonment. Characterization of temporal trends was carried out using logistic regression methods. Stratification was used to describe possible heterogeneities of the temporal trends according to cofactors.

Results: The overall prevalence of HIV and HCV were 55% and 88%. Average age was 20 years with a mean duration of injecting drug use of 7.6 years and 81% were males. Adjusted by duration of IDU, sex and age at initiation, the prevalence of HIV infection has dramatically declined (p < 0.001) : relative to 1999-2001, the odds of HIV infection was 9.4, 5.6, 2.7 and 1.5 higher in the preceding four periods of three years each from 1987 to 1998. The substantially higher prevalence of HCV has also shown a decline (p = 0.065) but of lesser magnitude. For each year of IDU, the odds of HIV and of HCV infection increased (p  <0.001) by 21 and 26% respectively. The decline of HIV infection was consistenly observed up to a duration of 10 years but it was not present among those with a duration longer than 10 years. In turn, the decline of HCV was restricted to those with short duration of IDU (< 4 years) because the prevalence was close to 100% for durations longer than 4 years in all calendar periods.

Conclusions:  AIDS awareness, preventive interventions and substance abuse treatment  have contributed to the current stabilization of HIV epidemic in Spain. However, the extremely high levels of HCV infection and the underlying prevalence of HIV may lead to a large health burden of end-stage liver disease among (ex-)IDU over the coming years.

Keywords: HIV-1; temporal trends; injecting drug users