Mpox in people living with HIV in Brazil: spatial distribution, clinical features, and outcomes from a nationwide surveillance study.

Background: Brazil has emerged as one of the global epicenters of the Mpox outbreak and accounts for the highest HIV prevalence in Latin America, particularly among men who have sex with men (MSM). Despite this overlapping epidemiological burden, population-based evidence on the intersection between Mpox and HIV remains limited. This study provides the first national epidemiological characterization of Mpox/HIV coinfection in Brazil, focusing on spatial distribution, clinical features, and outcomes. Methods: We conducted a nationwide, registry-based, retrospective, analytical cross-sectional study using individual-level data from Brazil's national surveillance system, encompassing all confirmed and probable Mpox cases reported between May 2022 and April 2025. Extracted variables included sociodemographic data, gender identity, sexual behavior, probable transmission route, STI coinfections, clinical presentation, hospitalization, and mortality. We calculated municipality-level cumulative case-notification rates of Mpox/HIV coinfection per 100,000 inhabitants using 2022 IBGE population estimates, mapped spatial distribution, and applied empirical Bayes smoothing. Group comparisons by HIV status used the Mann-Whitney and two-proportion Z tests (p < 0.05), with effect sizes estimated using rank-biserial correlation and Cohen's h, respectively. Analyses were conducted in R. Findings: Among 14,340 Mpox cases, 5031 (35.1%) occurred in people living with HIV (PLHIV), with disproportionate clustering in large urban centers and touristic municipalities. Individuals with Mpox/HIV coinfection had a median age of 34 years (interquartile range: 29.0-40.0) and were older, predominantly cisgender MSM, more often reported sexual contact as the probable route of exposure, and exhibited higher rates of other STIs, especially syphilis. Although certain symptoms, such as fever, fatigue, lymphadenopathy, myalgia, and mucocutaneous lesions, were more common among PLHIV, effect sizes were small, limiting their clinical discriminative value. Despite modest differences, PLHIV had also higher rates of antiviral therapy use against Mpox, hospitalization and ICU admission, and accounted for 93.3% of Mpox-related deaths. Interpretation: These findings support the integration of HIV status into Mpox surveillance and clinical protocols, especially in contexts marked by structural and social vulnerability. Funding: None.