Keywords
One health
prevention
outbreak
immunization
Abstract
BACKGROUND: Yellow fever, a mosquito-borne viral disease, is transmitted to humans through bites from infected mosquitoes. Bayelsa State, in Southern Nigeria, reported an outbreak of yellow fever in 2024 despite immunization efforts. This study outlines the outbreak findings and lessons learned.
METHOD: A secondary analysis of case-based surveillance data obtained from IDSR OO1C was conducted from January to December 2024, focusing on demographics such as age, sex, location, and time. Immunization coverage and entomological findings were also assessed.
FINDINGS: From January to December 2024, 85 suspected yellow fever cases were reported, 13 (15.29%) of which were presumptively positive and 6(7.06%) confirmed using RT-PCR and PRNT. Among suspected cases, 43(50.59) were males with an average age of 19.21 years and SD of ± 16.33. One death was reported amongst confirmed cases, giving a case fatality rate (CFR) of 16.7%. Among the six confirmed cases, one case each were identified in four LGAs of the state (Yenagoa, Southern Ijaw, Nembe and Brass), while two cases were reported in one LGA (Kolokuma/Opokuma). The January 2023 mass immunization campaign achieved 87% coverage. Entomological surveys in 5 communities, including areas with confirmed cases, identified three Aedes species (Aedes albopictus, Ae. luteocephalus, and Ae. simpsoni complex). Larval indices indicated a high epidemic risk across surveyed areas.
CONCLUSION: The findings show that while surveillance and vaccination remain important, robust environmental and vector control measures are essential for effective yellow fever prevention.
References
Guarner J, Hale GL. Four human diseases with significant public health impact caused by mosquito-borne flaviviruses: West Nile, Zika, dengue and yellow fever. Semin Diagn Pathol. 2019 May 1; Emerging infections issue36(3):170–6. doi:10.1053/j.semdp.2019.04.009
Musso D, Rodriguez-Morales AJ, Levi JE, Cao-Lormeau VM, Gubler DJ. Unexpected outbreaks of arbovirus infections: lessons learned from the Pacific and tropical America. Lancet Infect Dis. 2018 Nov 1;18(11):e355–61. doi:10.1016/S1473-3099(18)30269-X PubMed PMID: 29934112.
Monath TP, Vasconcelos PFC. Yellow fever. J Clin Virol. 2015 Mar 1;64:160–73. doi:10.1016/j.jcv.2014.08.030
Mensah EA, Gyasi SO, Nsubuga F, Alali WQ. A proposed One Health approach to control yellow fever outbreaks in Uganda. One Health Outlook. 2024 May 23;6(1):9. doi:10.1186/s42522-024-00103-x
WHO. Yellow fever [Internet]. 2023 [cited 2025 Aug 30]. Available from: https://www.who.int/news-room/fact-sheets/detail/yellow-fever
Ndeffo-Mbah ML, Pandey A. Global Risk and Elimination of Yellow Fever Epidemics. J Infect Dis. 2020 Jun 11;221(12):2026–34. doi:10.1093/infdis/jiz375
Gianchecchi E, Cianchi V, Torelli A, Montomoli E. Yellow Fever: Origin, Epidemiology, Preventive Strategies and Future Prospects. Vaccines. 2022 Feb 27;10(3):372. doi:10.3390/vaccines10030372 PubMed PMID: 35335004.
Servadio JL, Muñoz-Zanzi C, Convertino M. Estimating case fatality risk of severe Yellow Fever cases: systematic literature review and meta-analysis. BMC Infect Dis. 2021 Aug 16;21(1):819. doi:10.1186/s12879-021-06535-4
WHO. Yellow Fever – Nigeria [Internet]. 2021 [cited 2025 Sep 3]. Available from: https://www.who.int/emergencies/disease-outbreak-news/item/2021-DON336
NCDC. Nigeria Centre for Disease Control and Prevention [Internet]. 2019 [cited 2025 Sep 4]. An update of Yellow Fever outbreak in Nigeria. Available from: https://ncdc.gov.ng/diseases/sitreps/?cat=10&name=An%20update%20of%20Yellow%20Fever%20outbreak%20in%20Nigeria
NCDC. Nigeria Centre for Disease Control and Prevention [Internet]. 2024 [cited 2025 Sep 4]. An update of Yellow Fever outbreak in Nigeria. Available from: https://ncdc.gov.ng/diseases/sitreps/?cat=10&name=An%20update%20of%20Yellow%20Fever%20outbreak%20in%20Nigeria
Bayelsa State government Secretariat. Culture and Tourism | Bayelsa State [Internet]. 2024 [cited 2025 Sep 8]. Available from: https://bayelsastate.gov.ng/culture-and-tourism/
NCDC. National Guidelines for Yellow Fever Preparedness and Response [Internet]. 2019. Available from: https://ncdc.gov.ng/themes/common/docs/protocols/118_1581155661.pdf
Nwachukwu WE, Yusuff H, Nwangwu U, Okon A, Ogunniyi A, Imuetinyan-Clement J, et al. The response to re-emergence of yellow fever in Nigeria, 2017. Int J Infect Dis. 2020 Mar 1;92:189–96. doi:10.1016/j.ijid.2019.12.034 PubMed PMID: 31935537.
Ejikeme AR, Adeke AS, Uba N, Bunyoga D, Hassan S, Samson E, et al. Yellow fever outbreak in Ebonyi State, Nigeria, May-August 2019. PAMJ-One Health. 2022 Feb 9;7(18). doi:10.11604/pamj-oh.2022.7.18.32558
Adogo LY, Ogoh MO. Review Article: Yellow fever in Nigeria: A review of the current situation. Afr J Clin Exp Microbiol. 2020;21(1):1–13. doi:10.4314/ajcem.v21i1.1
WHO. Yellow Fever - West and Central Africa [Internet]. 2021 [cited 2025 Aug 30]. Available from: https://www.who.int/emergencies/disease-outbreak-news/item/yellow-fever---west-and-central-africa
Kassy WC, Ochie CN, Ndu AC, Agwu-Umuahi OR, Ibiok CN, Ogugua IJ, et al. A Systematic Review of Yellow Fever Outbreaks and Public Health Responses in Nigeria. Niger Med J J Niger Med Assoc. 64(4):427–47. doi:10.60787/NMJ-64-4-294 PubMed PMID: 38952887; PubMed Central PMCID: PMC11214706.
Akar SE, Nwachukwu W, Adewuyi OS, Ahumibe AA, Akanimo I, Okunromade O, et al. Epidemiology of Yellow Fever in Nigeria: Analysis of Climatic, Ecological, Socio-Demographic, and Clinical Factors Associated with Viral Positivity Among Suspected Cases Using National Surveillance Data, 2017–2023. J Epidemiol Glob Health. 2025 Jan 20;15(1):2. doi:10.1007/s44197-025-00341-w
This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.
Copyright (c) 2026 AUTHOR