Spatial analysis of confirmed lassa fever cases in Edo State, Nigeria, 2008-2014

Introduction: lassa fever (LF) is endemic and poses public health threats in Edo State. Identification of primary clusters (hotspot) will help prioritize public health interventions in the state. We investigated retrospective cases of LF to identify primary cluster of the disease for household exposure management. Methods: we reviewed retrospective data (n = 1400) of LF case-patients at a referral hospital in Edo State from 2008 to 2014 based on World Health Organization case definition for LF. We determined hotspot of confirmed cases on Bernoulli model and evaluated environmental factors in the hotspot: presence of rodent deterrents, proximity of households at 2 km radius to rice farm, rice postharvest storage facility, refuse dump, forest, hospital and main road using multi-criteria analysis at p < 0.05. Results: of the reviewed cases, 171 (12.2%) were confirmed case-patients. The median age of confirmed case-patients was 30 years (Q1: 16.0 and Q3: 43.5). Of the confirmed case-patients, 101 (59.1%) were male. Hotspot (4.45 km radius; geographic center at 6.717900°N, 6.243500oE) was identified in Esan West LGA. Associated environmental factors included proximities of households to refuse dump (p < 0.001), rice postharvest storage facility (p = 0.01) and rice farm proximity to households (p = 0.03) were significant to cases in Esan west. Conclusion: Esan West LGA was identified as a hotspot for lassa fever, household proximity to refuse dump sites, rice storage facilities and rice farms were associated to environmental factors. We recommend improved rice post-harvest storage, distancing rice farms from households and adhering to strict environmental sanitation in Edo State, Nigeria.