Mapping HTLV positivity in Colombia: insights from blood donor surveillance (2018–2024): Mapping HTLV positivity in Colombia: insights from blood donor surveillance (2018–2024)

Background: Since 2014, blood banks in Colombia have been required to screen 100% of collected donations for HTLV-1 and HTLV-2. Additionally, since 2011, confirmatory testing using immunoblot has been performed on donors with double reactivity. Individuals infected with HTLV have a lifetime risk of 0.25% to 4% of developing myelopathy or spastic paraparesis. Although most HTLV-1 carriers remain asymptomatic, the virus is associated with neoplastic diseases (adult T-cell leukemia/lymphoma), inflammatory syndromes, and opportunistic infections. The South American population is at higher risk of disease progression, with women being three times more likely to develop complications than men. Aims: To evaluate the HTLV positivity rate in Colombian blood Banks between 2018 and 2024. Methods: Data from the National Hemovigilance Information System (SIHEVI-INS) were analyzed from January 2018 to December 2024. The analysis included the total number of blood donations collected and screening results obtained through chemiluminescence, ELISA, and immunoblot testing in blood banks. Results: During the study period, 6,435,439 blood units were collected, of which 1859 tested positive for HTLV. Positivity rates varied across departments, suggesting a differential spatial distribution of the virus. Of the positive donations, 1,797 corresponded to individuals. The median age at detection was 41 years (IQR: 32–52). Among the positive donations, 659 were from male donors and 1,152 from female donors. The median time between blood donation and notification of HTLV positivity was 113 days (IQR: 82–186 days). In 8 departments, the median positivity rate was 5.7 (IQR: 4.7–8.7), with a total of 999,016 donations. In 12 departments, the median positivity rate was 2.8 (IQR: 2.6–3.1), with 2,270,575 donations. Finally, in the remaining 8 departments, the median positivity rate was 1.5 (IQR: 1.1–1.7), with 3,165,848 Summary/Conclusions: The data suggest that regions with higher HTLV positivity rates are also those with lower blood collection volumes. This finding raises the need to reconsider blood collection strategies in areas with high HTLV positivity rates, including the possibility of restricting collection in these locations to reduce transmission risk