Multiple introductions and sustained local transmission of Monkeypox virus in Southern Brazil between 2022-2023.

Mpox is a zoonotic viral disease caused by the Monkeypox virus (MPXV). Human cases have been mainly restricted to the African continent until the worldwide multi-country outbreak unfolded in 2022. We reconstructed epidemiological links of 53 MPXV infections using genomic epidemiology in Rio Grande do Sul State, southern Brazil, during 2022 and 2023. We detected five well-supported clades, three representing local transmission chains that were mostly restricted to the 2022 virus spread, one supported year-long maintenance encompassing samples from 2022 and 2023, and one new importation from Europe in 2023. Our results provide new insights into the geographic extent of community transmission and its association with viral diversity during the more pronounced 2022 mpox upsurge and during the following lower incidence phase. These findings highlight the power of continued genomic surveillance to uncover hidden transmission chains to understand viral dynamics and inform public health responses. The detection of sustained transmission in the state is important to guide targeted control measures to curtail further community and international transmission and highlight the need for maintaining genomic surveillance efforts.