Estimating Hepatitis C Burden In San Francisco: Quantifying The Disproportionate Impact On People Who Inject Drugs

Author: Grebe E, Facente SN, Burk K, Murphy EL, Mirzazadeh A, Morris MD, Smith AA,Sanchez MA, Evans JL, Nishimura A, Raymond HF

Theme: Epidemiology & Public Health Research Year: 2017

Background. Initiated in 2016, End Hep C SF is a comprehensive initiative to eliminate hepatitis C (HCV) infection in San Francisco. The introduction of direct-acting antivirals (DAAs) to treat and cure HCV provides an opportunity for elimination. To properly measure progress, a baseline estimate of HCV prevalence, and of the number of people in various subpopulations, including people who inject drugs (PWID), infected with HCV, is required to target and measure the impact of interventions.

Methods. Our estimates are based on triangulation of data found in case registries, medical records, cohort studies, and published literature from 2010 through 2017. We stratified the population by sex, age and/or HCV risk group, and estimated the population size and HCV prevalence in each group. When multiple sources of data were available, we calculated a weighted average using inverse variance weighting. Credible ranges (CRs) were derived from 95% confidence intervals of population size and prevalence estimates.

Results. We estimate that 23,311 residents of San Francisco are HCV seropositive (CR: 11,281 – 43,997), representing an overall seroprevalence of 2.7% (95% CI: 1.3% – 5.1%). Of these, 17,517 are estimated to be viremic (CR: 7,114 – 38,968), though this estimate includes treated cases. Despite representing only an estimated 2.8% of the population, PWID represent 69.9% of all viremic HCV infections: 12,253 cases (CR: 5,535 – 21,594). Seroprevalence in PWID is estimated at 65.3% (95% CI: 63.1 – 67.6%).

Conclusion. Our estimate provides a useful baseline against which the impact of End Hep C SF can be measured. PWID represent a large majority of viremic HCV cases, and elimination will require intensified targeted interventions for this group.

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