[Prevalence of HTLV-1 infection in family members of index cases in PeruPrevalência familiar da infecção pelo HTLV-1 a partir de um caso índice no Peru].

Objective: To estimate the prevalence of HTLV-1 infection among the family members of positive index cases referred to a specialized center in Peru and its distribution by type of relationship and presence of diseases associated with the infection. Methods: A retrospective study was conducted in which the records of the HTLV-1 Research Unit of the Alexander von Humboldt Institute of Tropical Medicine in Peru were reviewed. Index cases, defined as the first positive individual in each family group, were identified and the prevalence of HTLV-1 among their immediate family members (father, mother, siblings, children, and partners) was determined using a cluster estimator. Results: A total of 1255 index cases and 3431 family members were studied. The frequency among family members studied was 30.30%. The prevalence of HTLV-1 among family members was 36.43% (95% CI: 34.67-38.23) The specific frequencies were: 63.30% among mothers, 52.33% among fathers, 32.65% among siblings, 22.84% among children, and 57.19% among partners. Conclusion: The prevalence found suggests the existence of intrafamilial transmission in the cohort, which points to a need for further studies to identify associated risk factors. The findings highlight the need to implement a new screening strategy in the country in which close relatives of all HTLV-1-positive cases are tested. This approach should be reflected in public health policies.