Incidence of Treponema pallidum in donors from a blood centre in Colombia, 2012-2024.

Syphilis remains a significant transfusion-transmitted infection. In Colombia, routine epidemiological surveillance primarily targets pregnant women, leaving the burden of infection among the apparently healthy population. This study determined the incidence of Treponema pallidum and its associated factors in donors at a blood centre in Colombia between 2012 and 2024. A retrospective cohort study was conducted, analyzing 64,166 repeat blood donors. Incidence was calculated using 95% confidence intervals. Associations with demographic and donation-related variables were assessed using Chi-square test and potential confounders were adjusted using a multivariable regression model. The overall incidence of syphilis was 5.1 per 1,000 donors. The associated factors included age, sex, occupation, collection site, and donor type. Higher incidence proportions were observed in male donors (RR = 1.76), individuals aged between 60 and 65 years (RR = 2.43), unemployed individuals (RR = 3), donors collected at the centre (RR = 1.45), and replacement donors (RR = 3.51). These incidences indicate ongoing transmission within a low-risk population. The highest incidence in some groups enabled the generation of hypotheses about differential exposure patterns, guiding subsequent aetiological studies, and optimizing donor selection. Understanding local epidemiology is essential for designing public health interventions tailored to the specific epidemiological profile.