Epidemiology of Treponema pallidum and HIV co-infections in the Italian blood donor population: 2009-2021.

Background: In recent years, co-infection from HIV and Treponema pallidum has become more common. Early detection of the co-infection allows us to implement therapeutic strategies to control the evolution of the disease and to contain its transmission in the general population. The donor population is the target of choice for the detection of early-stage infections. This study aims to evaluate the trend of HIV/T. pallidum positivity in the Italian blood donor population, defining the type of donor most involved.

Materials And Methods: A retrospective analysis of consecutive blood donors' records, covering the period between January 2009 and December 2021, was conducted using the database of the National Blood Information System. The data extracted were the results of of confirmed positivity notifications for T. pallidum and sociodemographic variables of blood donors. The effect of age, female gender, donor category, year, and Italian origin on the probability of HIV/T. pallidum co-infection were estimated using a logistic regression model.

Results: In the period of observation, we found 79 subjects with HIV/T. pallidum dual co-infection, 3 with HIV/HCV/T. pallidum triple co-infections, and 2 with HIV/HBV/T. pallidum triple co-infections. Seventy-one out of 84 co-infections (89%) were among first-time tested donors, reporting sexual behaviors at risk. The results of the logistic regression show that age, female gender and regular donor status were not associated with HIV/T. pallidum co-infection.

Discussion: The transfusion network can provide a valid contribution to containing the spread of HIV and T. pallidum infections, raising the awareness of donors, and promptly referring the donor with confirmed positivity to the reference specialist.