Trends in hepatitis B virus, hepatitis C virus, and human immunodeficiency virus prevalence, risk behaviors, and preventive measures among Seattle injection drug users aged 18-30 years, 1994-2004

Injection drug users (IDUs) are at risk for infection with hepatitis B virus (HBV), hepatitis C virus (HCV), and human immunodeficiency virus (HIV). Information on time trends in prevalence of these viruses among IDUs and in behaviors influencing their transmission can help define the status of these epidemics and of public health efforts to control them. We conducted a secondary data analysis combining cross-sectional data from IDUs aged 18-30 years enrolled in four Seattle-area studies from 1994 to 2004. Participants in all four studies were tested for antibody to HIV (anti-HIV), hepatitis B core antigen (anti-HBc), and HCV (anti-HCV), and completed behavioral risk assessments. Logistic regression was used to investigate trends in prevalence over time after controlling for sociodemographic, drug use, and sexual behavior variables. Between 1994 and 2004, anti-HBc prevalence declined from 43 to 15% (p < 0.001), anti-HCV prevalence fell from 68 to 32% (p < 0.001) and anti-HIV prevalence remained constant at 2-3%. Declines in anti-HBc and anti-HCV prevalence were observed within the individual studies, although not all these declines were statistically significant. The declines in anti-HBc and anti-HCV prevalence remained significant after control for confounding. Although we did not observe coincident declines in injection equipment sharing practices, there were increases in self-reported needle-exchange use, condom use, and hepatitis B vaccination. We conclude that there has been a substantial and sustained reduction in prevalence rates for HBV and HCV infection among young Seattle IDUs, while HIV rates have remained low and stable.