The Urban Health Study recruited semiannual cross-sections of persons who injected illicit drugs from the streets and other natural settings in inner-city neighborhoods in the San Francisco Bay area.2
Of nearly 14,000 persons enrolled from 1986 through 2002, nearly 5,000 participated more than once (mean, 4.5 visits), comprising a passive, embedded cohort.3
Participants were interviewed, tested for HIV antibody, and given harm reduction counseling and referrals to needed services. Data from the interviews, blood samples, and add-on studies were used to study health and illness among persons who inject illicit drugs and evaluate interventions. Findings from this cohort have been published in more than 100 articles, describing basic biological, clinical, immunological, and epidemiologic investigations; social and behavioral studies; and research on health services, health policy, and legal policy.2-7
From 1998 through 2002, 4,018 study participants received hepatitis B and C serologic testing, of whom 3548 (88%) tested positive for antibodies to the hepatitis C virus (HCV). Of those testing negative, 84 returned for a subsequent visit, and 24 tested positive for HCV antibody, representing prospectively identified seroconversions. Retrospective testing of stored serum identified an additional 43 seroconversions during 1986-1998. Ongoing analyses are examining HCV prevalence, incidence, and risk factors, and genetic factors associated with resistance to viral infection and persistence.