Review maps interconnected drivers of Lassa fever in Nigeria

A systematic review of Lassa fever risk in Nigeria identifies converging factors across human, animal and environmental domains as central to persistent transmission. Drawing on 38 eligible studies published from January 2000 through March 2025, the review found that human behaviours and health-care conditions were the most consistently documented determinants, while the ecology of reservoir rodents and changes in the built and natural environment amplified opportunities for exposure. Lassa fever is a zoonotic viral haemorrhagic disease caused by Lassa virus and is endemic in multiple Nigerian states; the review reports that the country accounts for approximately 70% of the global disease burden.

The researchers followed PRISMA 2020 guidelines and searched five bibliographic databases—PubMed, Scopus, Web of Science, the African Journals Online database and Google Scholar—while also consulting grey literature. They included studies investigating at least one aspect of Lassa fever risk in Nigerian endemic areas and containing empirical data. Of 612 records identified, 38 met the eligibility criteria. Methodological quality was appraised with Critical Appraisal Skills Programme and Joanna Briggs Institute checklists, and findings were synthesized thematically. The protocol was registered with PROSPERO as CRD420261436085.

Among human risk factors, the studies most consistently reported open food storage, occupational exposure, poor household hygiene and nosocomial transmission in facilities without adequate infection prevention and control. The latter finding points to the role of health-care settings in allowing person-to-person transmission under deficient containment conditions. Animal evidence focused on the peri-domestic ecology of Mastomys natalensis, the rodent implicated as a reservoir of Lassa virus, with rodent density strongly correlated with human exposure. Environmental conditions—including poor housing, inadequate waste management, deforestation, climate variability and peri-urban expansion—were identified as contextual amplifiers of risk rather than isolated causes. The review’s evidence therefore supports an interconnected model in which human practices, reservoir populations and environmental change jointly shape transmission.

Spatial analyses in the included literature identified perennial hotspots in Edo, Ondo, Ebonyi and Plateau states, together with seasonal peaks at the end of the rainy season. The review also describes thousands of deaths during annual outbreaks, indicating that transmission has persisted despite the disease’s established endemicity. Because the evidence came from heterogeneous studies conducted across different locations and domains, the synthesis does not quantify a single population-wide effect or establish that every reported factor carries the same degree of importance. Instead, it shows that Lassa fever risk is shaped by several simultaneously operating determinants across human, animal and environmental systems.

The authors conclude that controlling Lassa fever requires an integrated One Health approach rather than reliance on any one intervention. They call for strengthened infection prevention and control, improved diagnostics, community-based rodent-proofing and sanitation programmes, coordinated surveillance across humans, animals and environments, culturally tailored risk communication and sustained domestic financing. The review does not test these measures in a clinical trial, nor does it demonstrate that the combined package will reduce deaths. Its contribution is to consolidate the available empirical evidence and characterize persistent endemicity as the outcome of converging determinants, providing a rationale for coordinated surveillance and prevention across Nigeria.

Subject of Research: Systematic review of human, animal and environmental risk factors for Lassa fever in endemic areas of Nigeria

Article Title: One health perspectives on Lassa fever: a systematic review of human, animal, and environmental risk factors in endemic areas of Nigeria

Article References: Olaiya, O., Akyala, A. I., Coker, O. S., Akanbi, K., Olatinwo, I. A., & Idoko, A. M. (2026). One health perspectives on Lassa fever: a systematic review of human, animal, and environmental risk factors in endemic areas of Nigeria. BMC Public Health. https://doi.org/10.1186/s12889-026-29334-5

Image Credits: AI Generated

DOI: 10.1186/s12889-026-29334-5

Keywords: Lassa fever, Nigeria, One Health, zoonoses, Mastomys natalensis, systematic review, rodent-borne viruses, infection prevention, environmental health, health, perspectives, Lassa