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Item Epidemiological insight into the possible drivers of Lassa fever in an endemic area of Southwestern Nigeria from 2017 and 2021(2023-09-08) Cadmus, SimeonBackground Lassa fever (LF) is a viral disease transmitted between animals and humans, commonly found in West Africa, including Nigeria. The region experiences an estimated annual total of about 2 million LF cases in humans, leading to 5,000 to 10,000 deaths. Strikingly, up to 80% of LF-infected individuals show no symptoms, making its true incidence hard to determine in endemic populations. We investigated LF distribution, mortality, survival patterns, and contributing factors during a local outbreak in Nigeria, from 2017 to 2021. Method Data from the Integrated Disease Surveillance and Response weekly line list for 2017 to 2021 were extracted. The survival pattern of LF patients was visualized with the Kaplan-Meier curve, binary logistic regression model was employed to explore LF-associated factors and level of statistical significance (α) was set at 5%. Result Overall, 4,554 participants were recruited between 2017 and 2021. Their average age varied from 31.82 ± 20.0 to 37.85 ± 17.89. LF-positive patients decreased from 26.9% in 2017 to 17.7% in 2021, paralleling the mortality trend. In 2021, patient survival ranged from 5 to 30 days. Male patients had lower survival odds in the initial 10 days of hospitalization, improved chances from days 10 to 20, and reduced probabilities beyond day 20. Residence location and age were significant factors (p<0.05) associated with LF in Ondo State. Conclusion The decline in LF cases in 2021 could be attributed to the ongoing intervention by Nigerian Centre for Disease Control or the disruption caused by the COVID-19 pandemic in 2020. To address LF challenges in hotspot areas, we propose Community Action Networks that would operate using the One Health approach involving local stakeholders sustainably to promote Early Warning/Early Response system in high-risk settings and mitigate LF-related issues. SUMMARY Lassa fever (LF) is an important disease of global public health concern that is endemic in West Africa. In Nigeria, the disease constitutes a major health challenge with outbreaks being recorded on an annual basis despite efforts channeled towards combating it by the government at various levels. This study analysed a five years data of LF in Ondo State southwestern Nigeria. The results identified age and location were identified as important factors associated with infection and mortality among LF patients as the incidence and case fatality rates were highest among adults (≥ 45 years), while the highest number of suspected, confirmed and dead cases was recorded in Owo Local Government Area. Furthermore, we identified drying of food items by the roadside where rodent vectors can access them, presence of a local market, poor and unsafe sewage disposal, and proximity of refuse dumps to residential areas as possible socio-ecological factors/practices fueling the endemicity and seasonal outbreak of LF. These findings emphasize the need for active involvement of community members in the already established national LF surveillance network to facilitate prompt case identification, and early reporting and response in the LF-endemic areas of the country.Item Ecological correlates and predictors of Lassa fever incidence in Ondo State, Nigeria 2017–2021: an emerging urban trend(Nature Portfolio, 2023-11-27) Cadmus, SimeonLassa fever (LF) is prevalent in many West African countries, including Nigeria. Efforts to combat LF have primarily focused on rural areas where interactions between rodents and humans are common. However, recent studies indicate a shift in its occurrence from rural to urban areas. We analysed secondary data of reported LF outbreaks from 2017 to 2021 in Ondo State, Nigeria to identify the distribution pattern, ecological variations, and other determinants of disease spread from the ward level using nearest neighbour statistics and regression analysis. Data utilised include LF incidence, ecological variables involving population, nighttime light intensity, vegetation, temperature, market presence, road length, and building area coverage. ArcGIS Pro 3.0 software was employed for spatial analysis. Results revealed spatio-temporal clustering of LF incidents between 2017 and 2021, with an increasing trend followed by a decline in 2021. All wards in Owo Local Government Area were identified as LF hotspots. The ecological variables exhibited significant correlations with the number of LF cases in the wards, except for maximum temperature. Notably, these variables varied significantly between wards with confirmed LF and those without. Therefore, it is important to prioritise strategies for mitigating LF outbreaks in urban areas of Nigeria and other LF-endemic countries.Item Drivers of Lassa fever in an endemic area of southwestern Nigeria (2017–2021): An epidemiological study(Public Library of Science, 2025-06-25) Cadmus, SimeonBACKGROUND: Reporting two million human Lassa fever (LF) cases with around 10,000 associated annual mortality, the West African sub-region is endemic for Lassa fever virus (LASV). The true incidence of LF is difficult to determine because most LASV-infected individuals show no differentiating clinical signs and symptoms. We investigated the distribution of cases, post-hospitalization survival patterns, and evaluated factors contributing to infection and clinical course of the disease during an outbreak of LF in Ondo State, Nigeria, from 2017 to 2021. METHODS: We extracted LF data from the Integrated Disease Surveillance and Response weekly report of the Nigerian Centre for Disease Control for 2017-2021. Kaplan-Meier estimate was used to describe the probability of survival among the LF cases. Also, a univariable binary logistic regression was used to explore factors associated with mortality among the study participants. Key informant was interviewed and environmental assessments were also done. RESULTS: LASV infection was confirmed in 1,115 (24.5%) of 4,551 cases with clinical signs suggestive of LF (age 35.24 ± 20.77) and case fatality rate of 25.5%. Hospitalized patients who did not recover within 17 days had less than 50% chance of survival. Age is a strong predictor of survival; hospitalized patients >40 years were significantly more likely than younger ones to experience mortality (Odds ratio:2.46; 95% CI = 1.67-3.62; p < 0.01). Similarly, male patients were significantly less likely than the females to survive beyond 10 days of hospitalization. Open sun drying of food items and congested urban residential settings with history of frequent rat sightings are possible factors for the increase of LF cases in the study area. CONCLUSION: Current case definition in Ondo State identified close to 25% of laboratory confirmed LASV infection. Human activities during the dry season (October-March) are associated with increased LF cases. We propose a One Health disease surveillance approach that synchronizes farming activities with educational campaigns as a mitigation strategy against LASV infection and mortality in Nigeria.