Abstract
BACKGROUND: The HTLV-1 affects 5 to 10 million people worldwide. It is estimated that 5 to 10% of the infected individuals develop severe diseases, such as HTLV-Associated Myelopathy/Tropical Spastic Paraparesis (HAM/TSP) or Adult T-Cell Leukaemia/Lymphoma (ATLL). HTLV-1 transmission can occur mainly through unprotected sexual contact and from mother to child during breastfeeding. No vaccines can contain this infection, and strategies to prevent transmission become a priority. Therefore, it is important to know the main dissemination routes of each region to design the best public health strategies for controlling the spread of this virus. OBJECTIVES: This study aimed to evaluate the prevalence of family aggregation in HTLV-1 infection among patients treated at a reference centre in Brazil. METHODS: A cross-sectional study was conducted with patients between July 2021 and August 2022. A total of 67 individuals were attended, of which 17 were classified as index cases due to a history of family aggregation, with 120 family contacts. FINDINGS: We found a prevalence of 36% of individuals positive for HTLV-1 and the same for HTLV-1 negative, while 28% of the family members had unknown serology. The possible transmission routes were identified, and the familial transmission histories within each family were hypothesised. MAIN CONCLUSIONS: These data can support specific decisions regarding the local reality, such as a better health strategy, especially in preventing new HTLV-1 cases.