Emergence of West African Human T-Lymphotropic Virus 1aC Subgroup, Brazilian Amazon

The emergence of West African human T-lymphotropic virus 1aC (HTLV-1aC) subgroup was identified in the Brazilian Amazon during a survey in Manaus. The study included 1,397 residents of Manaus who were tested for HTLV-1/2 antibodies between May 2021 and November 2023. The overall seroprevalence of HTLV-1/2 was 0.3% (4 out of 1,397 participants), comprising 3 HTLV-1 and 1 HTLV-2 infections. All seropositive participants were older than 40 years of age and belonged to a socioeconomically vulnerable population, with 75% being female. Phylogenetic analysis confirmed the presence of HTLV-1aC subtype, providing evidence of the introduction of West African HTLV-1aC into the Brazilian Amazon. The findings highlight the need for improved genomic surveillance in the region.