An outbreak of hepatitis B virus infection among methamphetamine injectors : the role of sharing injection drug equipment

Aim  To identify risk factors for acute hepatitis B virus (HBV) infection among Wyoming methamphetamine injectors. Design  A case–control study conducted in the setting of an outbreak. Setting  A county in central Wyoming, United States. Participants  Cases were identified through surveillance and contact tracing and were defined as Natrona County, Wyoming, residents who were either symptomatic or confirmed serologically to be acutely infected with HBV during January–August, 2003. Controls were susceptible to HBV infection. All participants identified themselves as methamphetamine injectors. Measurements  Participants were administered a survey that inquired about risk factors for HBV infection, including drug use practices and sexual behaviors. Controls were also tested serologically for acute HBV infection. Findings  Among the 18 case-patients and 49 controls who participated in the study, sharing water used to prepare injections and/or rinse syringes was associated with HBV infection (94% of case-participants versus 44% of controls; OR = 21.9, 95% CI: 2.7, 177.8), as was sharing cotton filters (89% of case-participants versus 52% of controls; OR = 7.4, 95% CI: 1.5, 35.6); sharing syringes was not statistically associated. In logistic regression models adjusted for age, sex, and interview site, sharing rinse water and sharing cotton remained statistically associated. Conclusions  Methamphetamine use has become increasingly prevalent in the United States. Our findings highlight the need for awareness of risks associated with injection drug use and sharing behaviors. Enhanced hepatitis B vaccination programs and educational campaigns that target methamphetamine injectors specifically, including those living in rural areas, should be developed and implemented.