Fourfold or higher mpox mortality in people living with HIV: A national cohort from Sierra Leone's 2025 outbreak

Introduction: People living with HIV (PLHIV) with immune compromise may face a higher risk of severe mpox, but African outbreak data remain limited. Methods: We conducted a retrospective national cohort study of laboratory-confirmed mpox cases in Sierra Leone from 9 January to 26 November 2025. Surveillance records were linked to HIV programme registers in DHIS2. Mpox-attributable death was the primary outcome. Logistic regression estimated adjusted odds ratios (aOR) adjusted for age, sex, and district. Among PLHIV, mortality was stratified by viral suppression (<1,000 copies/mL) and CD4 count (<200 vs ≥200 cells/µL) using Fisher’s exact test. Results: Of 5,442 confirmed cases, 4,891 (89.9%) had documented HIV status; 426 (8.7%) were PLHIV. Mortality was higher in PLHIV than in HIV-negative individuals (15/426, 3.5% vs 38/4,465, 0.9%; aOR 3.72; 95% CI: 1.98-6.99; p<0.001). Among 312 PLHIV with viral-load data, mortality was 13.8% (9/65) in unsuppressed PLHIV and 0.8% (2/247) in virally suppressed PLHIV (OR: 19.7; p<0.001). Among 286 PLHIV with CD4 data, mortality was 15.4% (8/52) with CD4 <200 cells/µL and 1.3% (3/234) with CD4 ≥200 cells/µL (OR: 14.0; p<0.001). In seven districts, ART-clinic vaccination coverage reached 71.0% within six weeks. Conclusion: Excess mpox mortality in PLHIV was concentrated in those with unsuppressed viral load (OR 19.7) or CD4 <200 cells/µL (OR 14.0), while virally suppressed PLHIV had mortality similar to HIV-negative individuals. Findings support using HIV treatment and immune status to prioritise risk assessment, monitoring, and vaccination through ART clinics.