High Incidence, Re-Infections, and Active Syphilis in Populations Attending A Specialized HIV Clinic in Mexico, A Dynamic Cohort Study.
Abstract Background. Syphilis has reemerged in many vulnerable groups around the world. The objective of the current study was to determine the prevalence and incidence of syphilis among people who attended a specialized HIV clinic in Mexico from 2011-2015.Methods. Databases from the laboratory were analyzed and four groups were formed: people seeking HIV-1 voluntary counseling and testing (VCT), people in prison (PPr), people living with HIV (PLWH) and patients from primary care clinics (others). Syphilis diagnosis was made using the reverse algorithm; antibody titers were examined to determine the stage of infection. Baseline data was analyzed, and with follow-up information, a retrospective dynamic cohort was formed. Factors associated with seroprevalence of syphilis and active syphilis were evaluated by the chi-square test. Moreover, risk factors for the incidence of syphilis were described. Results. A total of 81,863 baseline individuals were analyzed. Syphilis seroprevalence was 9.9% in VCT, 8.2% in PPr, 37.0% in PLWH, and 8.7% in others; the prevalence of active syphilis was 1.7-13.1%. A total of 11,124 people were followed-up; the incidence (cases per 100 years people) was 3.5 among VCT and 16.0 among PLWH; moreover, the frequency of re-infections was 11.1-24.4%. Men, transgender, persons between 20-39 years old, and individuals with a history of HIV or hepatitis B had a higher risk of syphilis. Conclusions. Several vulnerable groups have exhibited a reemergence of syphilis, with high prevalence of active syphilis, high incidence, and re-infections. Persons living with HIV had the highest risk.