A 2,022-patient acute-fever study in Mali finds dengue is now the most frequently detected pathogen, with three virus serotypes co-circulating and chikungunya, West Nile, and Rift Valley fever viruses also detected. Published in PLoS Neglected Tropical Diseases, it identifies Mali as a multi-pathogen arbovirus hotspot for the Sahel.
A cohort study published on 8 July 2026 reports new evidence on dengue emergence in the Sahel. The Doumbia et al. paper in PLoS Neglected Tropical Diseases combines two cohorts. The first is a 2016 to 2022 retrospective cohort of 210 patients. The second is a 2023 to 2024 prospective cohort of 1,812 patients.
Together they form a 2,022-patient acute undifferentiated fever dataset from health centres and hospitals in Mali, mainly Bamako. The headline finding is a 5x rise in dengue detection rate, from 7.6 percent retrospective to 29.5 percent prospective. Three DENV serotypes (DENV-1-III, DENV-2-II, DENV-3-III) all co-circulate in Mali, and their phylogenetic lineages originate in the subregion. The cohort also reports 7 chikungunya, 2 West Nile virus, and 1 Rift Valley fever virus cases. These findings identify Mali as a multi-pathogen arbovirus hotspot for the Sahel and West Africa.
What Doumbia and colleagues measured
Doumbia and colleagues led the study. The authors work at the Laboratory for Applied Molecular Biology (LBMA) at the Campus de Badalabougou. It is part of the University of Sciences, Techniques and Technologies of Bamako (USTTB). They also work with the Unité des Virus Émergents consortium at Aix-Marseille Université.
The consortium includes Università di Corsica, Institut national de la santé et de la recherche médicale, and Institut de Recherche Biomédicale des Armées. The Centre National de Référence des Arbovirus, at the same Marseille institutions, and Clinique Espoir in Bamako also contributed. The paper appeared in PLoS Neglected Tropical Diseases on 8 July 2026 (DOI: https://doi.org/10.1371/journal.pntd.0014494, PMID 42418522).
The team screened 2,022 patients with acute fever lasting under 7 days. The patients presented to health centres and hospitals in Mali, mainly Bamako. The study covered a 2016 to 2022 retrospective cohort of 210 patients and a 2023 to 2024 prospective cohort of 1,812 patients. The prospective sub-study excluded pyogenic, urinary, tuberculosis, viral hepatitis, typhoid fever, and post-traumatic infections. Blood samples were tested by molecular detection with serotyping and genomic sequencing. The team collected demographic data and malaria results for all patients, and clinical data prospectively.
Dengue virus was the most frequently detected pathogen in the cohort: 7.6 percent (16 of 210) retrospectively and 29.5 percent (535 of 1,812) prospectively. The authors report that the prospective detection rate is the highest in any African cohort published to date. It represents a 5x increase from the retrospective to the prospective period. The authors attribute the rise to improved diagnostic capacity, active surveillance, and the recent emergence of the DENV-1-III, DENV-2-II, and DENV-3-III lineages in the subregion. Three serotypes were identified: DENV-2 (n=185), DENV-1 (n=113), and DENV-3 (n=105); 148 DENV cases could not be typed. All three DENV serotypes co-circulate in Mali, and repeat exposure to different serotypes raises the risk of severe dengue through antibody-dependent enhancement.
The phylogenetic analyses showed a recently emerging lineage for each serotype, with DENV-1-III, DENV-2-II, and DENV-3-III all originating in the subregion. The cohort also detected 7 chikungunya, 2 West Nile virus, and 1 Rift Valley fever virus cases. These findings identify Mali as a multi-pathogen arbovirus area for the region.
The clinical profile is consistent with the diagnostic challenge of acute undifferentiated fever in the Sahel. The most frequent symptoms are headache, asthenia, arthralgia, myalgia, and back pain. Symptom burden was significantly higher in dengue patients than in non-dengue acute undifferentiated fever presentations. Unlike malaria, dengue detection rates were higher in patients over 18. That pattern is consistent with the childhood-immunity model for endemic dengue in sub-Saharan Africa, where adults carry the first-exposure severe-dengue risk. Outcomes include 6 haemorrhagic dengue cases, no deaths, and no intensive-care transfers, consistent with early detection and clinical management in the prospective design.
The authors conclude that the findings confirm the burden of arbovirus infections in Mali and the growing dengue burden on public health. They write that dengue monitoring is a major challenge in sub-Saharan countries and that it should inform future vaccination policy.
What the study adds
The Doumbia paper is the first combined retrospective and prospective acute undifferentiated fever cohort study of this size for Mali. Its practical point is that clinicians in Mali should consider dengue in patients with acute fever, not only malaria.
What the study does not claim
The paper does not criticise any vaccine, biocontrol, or vector-control programme. It does not use emergency framing for dengue in the Sahel. It does not claim that 2026 will bring a dengue surge across the subregion.
The paper's emphasis is on surveillance and diagnostic capacity, not on any failure of vaccines or vector control.
What to watch
Dengue surveillance in Mali and across the Sahel remains limited. The authors call for better monitoring to inform diagnosis and future vaccination policy.
Published 2026-07-10 · Mosticare Editorial
This article is general information, not medical advice. Ask a doctor or pharmacist about your own health.