Surveillance for acute hepatitis C virus (HCV) infection is difficult as only 25% of patients have gastrointestinal symptoms or jaundice, and diagnostic tests cannot distinguish it from chronic infection. From 2003-2011, the Philadelphia Department of Public Health (PDPH) identified ~1 acute HCV case/year via provider report. In 2011, PDPH obtained funding enhancing hepatitis surveillance. Resources and strategies for acute HCV surveillance vary greatly at health departments yet inform the national surveillance estimate. This study quantifies the number of cases found as a result of enhanced surveillance and the adherence to national case definitions.
METHODS:
The PDPH hepatitis registry houses reported HCV tests and associated liver function test (LFT) results for Philadelphia residents. For 2012–2015, acute HCV case finding, which traditionally relied upon provider report and healthcare associated outbreak investigations, was supplemented by investigating cases meeting enhanced criteria: 1) LFT results ≥200 U/L, 2) age ≤30 or >75 years, 3) hemodialysis center laboratory report 4) negative HCV RNA report with a previous positive test, and 5) seroconversions (negative HCV-antibody results matched quarterly to the registry). Potential cases were assessed for symptoms of acute hepatitis infection and the adherence to 2012 and/or 2015 CSTE acute HCV case definitions.
RESULTS:
From 2012-2015, PDPH identified 115 acute HCV cases fitting the 2015 case definition, 84 (73%) of which fit the 2012 case definition, and 3 (2%) of which were reported by a provider. This is 29 times the annual reported rate in 2003-2011. Thirty-five cases were identified based on age, 55 by 12 month seroconversion, 13 cases by the remaining enhanced criteria, and 12 through investigation of a systematic sample of new HCV laboratory cases. Thirty-three percent (n=38) of cases were jaundiced, and 83% of acute cases could be identified by investigating seroconversion in 12 months and/or LFTs >200 IU/L. An additional 36 individuals were identified with acute signs/symptoms but did not satisfy either CSTE case definition.
CONCLUSIONS:
The case finding methods used in this study identified a large number of acute HCV. These data demonstrate the scale at which acute infection has been dramatically underestimated. While the 2015 CSTE case definition is more permissive than the 2012 version, acquisition of additional laboratory tests and prioritization of specific populations for follow-up are necessary to further enable acute case finding. This study shows additional resources will be required to identify acute HCV cases and develop a more accurate national estimate of this disease.