Examination of HCV & STD Co-Infection and Co-Occurrence At ZIP Code Level

Background: The overlap between the hepatitis C virus (HCV) and STD has not been previously explored in Philadelphia. This is partially due to the separate disease surveillance systems, but also because the epidemiology of these diseases is often quite different. Examination of disease co-infection and co-occurrence can help identify opportunities for service integration, as well as gaps in testing and reporting.

Objectives: To estimate rates of HCV-STD co-infection and co-occurrence at the ZIP code level.

Methods: Surveillance data for HCV and STD for 2000-2010 were extracted from separate surveillance systems. Due to the high prevalence of reported Chlamydial infections, this project focused on reports of syphilis and gonococcal (GC) infections. For co-infections, reports were matched by name and date of birth. ZIP code-level disease rates were calculated and categorized as high (exceeding average rate by two standard deviations) or not. ZIP codes with high rates of two infections were considered to have high co-occurrence rates. 

Results: Of the 54 Philadelphia ZIP codes, three zip codes were identified with high co-occurrence rates of at least one STD and HCV (one with HCV-GC, and two with HCV-syphilis). None of these three ZIP codes had high rates of co-infection with these same infections.  There were two ZIP codes with high co-infection rates of HCV-GC and HCV-syphilis; one ZIP code with high rates of HCV-GC and one ZIP code with high rates of HCV-syphilis.

Conclusions: The lack of correlation between co-occurrence and co-infection indicates either missed screening opportunities for HCV, surveillance system gaps, or the actual co-infection rate of HCV and GC and syphilis are low.

Implications for Programs, Policy, and Research: Such analyses can be part of larger efforts to identify localized geographic areas to focus targeted screening, provider education, and other efforts to allow for more comprehensive disease management and surveillance.