Epidemiological serosurvey and molecular characterization of sexually transmitted infections among 1890 sheltered homeless people in Marseille: Cross-sectional one day-surveys (2000-2015)

Objectives: We observed the prevalence and distribution of potential risk factors for sexually transmitted infections (STIs) among Marseille homeless population.

Methods: Over the 2000-2015 period, we enrolled 1890 sheltered homeless adults and collected serum samples. Markers of hepatitis B and C viruses (HBV, HCV) and Treponema pallidum were searched using the CMIA testing. Positive HBsAg or anti-HCV samples underwent sequencing; positive anti-T. pallidum sera were subjected to the RPR test.

Results: The overall prevalence of HBsAg, anti-HBs, anti-HBc, anti-HCV and anti-T. pallidum (by CMIA and RPR) was 4.1%, 22.9%, 35.5%, 5.3% and (6.8%, 1.0%), respectively. We found a significantly higher prevalence of HBsAg and anti-T. pallidum among individuals born in sub-Saharan Africa (or Asia) compared to those born in Europe. Being older (>42 years), toxicomania status, cannabis use and underweight status (compared to normal status) were independent factors associated with HCV seropositivity. Using sequencing, we obtained a substantial diversity of HBV and HCV genotypes. One HCV sequence harbouring a L31M substitution in the NS5a protein may be associated with reduced drug sensitivity.

Conclusions: The positive relationship between toxicomania and HCV suggests the need for effective prevention programmes including health education activities and addiction treatment.