Original Articles
Vol. 2 No. 3 (2026)
https://doi.org/10.4081/sjroh.2026.657

Emerging and re-emerging infectious diseases in the Sahel: a One Health investigation of an influenza A(H1N1)pdm09 outbreak in the Abéché Health District, Chad, 2021

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Published: 7 October 2026
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Influenza A(H1N1)pdm09, emerging disease, One Health, case-control study, epidemiological surveillance, Chad, Sahel, zoonosis

Authors

Oumaima Mahamat Djarma
oumidj@yahoo.fr
Department of Infectious Diseases, La Référence Nationale University Hospital Center, N’Djamena, Chad.
Madina Hadjer
Livestock Research Institute for Development, N’Djamena, Chad.
Leandre Kampala
World Health Organization Regional Office for Africa, Brazzaville, Congo.
Narassem Mbaidoum
Ministry of Public Health and Prevention, N’Djamena, Chad.
Fatimé Abdelrazack
Livestock Research Institute for Development, N’Djamena, Chad.
Abdelsadick Hidjab
Ministry of Public Health and Prevention, N’Djamena, Chad.
Ali Abderaman Abdoulaye
Faculty of Human Health Sciences, University of N’Djamena, Chad.
Abdelmahmoud Chêne
Ministry of Public Health and Prevention, N’Djamena, Chad.
Oumar Ramadan
Ministry of Public Health and Prevention, N’Djamena, Chad.
Abdoulaye Moustapha
Ministry of Public Health and Prevention, N’Djamena, Chad.
Mahamat Ali Bolti
Livestock Research Institute for Development, N’Djamena, Chad.
Alain-Bruno Bardiguyo Allaramadji
Department of Infectious Diseases, La Référence Nationale University Hospital Center, N’Djamena, Chad.
Marc Mbaitoloum
Faculty of Human Health Sciences, University of N’Djamena, Chad.
Idriss Mahamat Mai
Faculty of Human Health Sciences, University of N’Djamena, Chad.
Tchonfiene Paasiri
Faculty of Human Health Sciences, University of N’Djamena, Chad.
Ali Mahamat Moussa
Faculty of Human Health Sciences, University of N’Djamena, Chad.
Mahamat Fayiz Abakar
Livestock Research Institute for Development, N’Djamena, Chad.

Emerging infectious diseases threaten global health security, particularly where integrated human-animal-environment surveillance is limited. In May 2021, Chad reported an influenza-like illness (ILI) outbreak in the Abéché Health District (Ouaddaï Province) following unusual avian mortality. We conducted a One Health investigation from May 1 to June 24, 2021, combining active case finding, a neighborhood-matched case-control study (58 cases, 58 controls) of warthog- and poultry-related exposures, an animal/environmental investigation, and virological testing (quantitative reverse transcription polymerase chain reaction [RT-qPCR] in humans; hemagglutination inhibition in poultry). We identified 210 ILI cases, 77.6% in the Amtiab villages (Abéché Health District); children under 10 were the most affected, with one death (probable encephalitis, age 13). Age under 15 years (odds ratio [OR]=4.49, 95% confidence interval [CI]: 1.61-12.55) and contact with a case (OR=4.39, 95% CI: 1.89-10.21) were significantly associated with ILI. RT-qPCR confirmed A(H1N1)pdm09 in humans; poultry showed prior mortality and anti-H9N2 antibodies, without an established causal link. This investigation rapidly identified an A(H1N1)pdm09 outbreak in a rural Sahelian setting where human-wildlife-poultry cohabitation and poor sanitation favor zoonotic pathogens. Young age and close contact drove the transmission. Strengthened integrated influenza surveillance and diagnostic capacity are needed in sub-Saharan Africa.

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How to Cite



Emerging and re-emerging infectious diseases in the Sahel: a One Health investigation of an influenza A(H1N1)pdm09 outbreak in the Abéché Health District, Chad, 2021. (2026). Sahelian Journal of Responsible One Health, 2(3). https://doi.org/10.4081/sjroh.2026.657
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