Trend and factors associated with Lassa Fever in Nigeria: A laboratory based retrospective data review, 2009–2018

Abstract

Background: Lassa Fever (LF) is associated with high morbidity and mortality. In recent years, outbreaks of LF have occurred annually in Nigeria. Edo State has been shown to be one of the hot spots of these outbreaks. Laboratory confirmation of LF is critical in the control and management of outbreaks. We analyzed laboratory based LF data to assess the pattern, burden and distribution of confirmed LF cases. Methods and materials: We carried out a 10-year retrospective analysis of laboratory based LF dataset obtained from the Institute of Lassa Fever Research and Control Laboratory, Irrua Specialist Teaching Hospital, Irrua, Edo State. Variables analysed include age, gender, polymerase chain reaction (PCR) results, symptoms at presentation and clinical outcome. We carried out descriptive analysis of abstracted variables and calculated frequencies and proportions. Bivariate analysis was carried out to show associations. Confidence interval was set at 95%. Results: During the review period, 14,822 records were analyzed from all sample records received in the laboratory. Of these, 1696 (11.4%) were positive for LF. Median age of positive cases was 32 years (Range: 1 day–106 years). Of the positive cases, 967 (57%) were males. Age-group 20–39 was most affected. Symptoms identified among confirmed cases include fever 1423 (83.9%), headache 790 (46.6%), abdominal pain 643 (37.9%), vomiting 399 (23.5%), bleeding 246 (14.5%). Number of positive cases increased from 139 in 2009, 156 in 2012 to 572 in 2018. Samples received from males (AOR: 1.29, 95%CI: 1.16–1.43) or from those older than 30 years (AOR 1.15, CI: 1.03–1.27) were more likely to test positive. Conclusion: With a steady increase in cases of LF over the years, high index of suspicion by health workers, early diagnosis of Lassa Virus (LV) in suspected cases are key. We recommend increased sentization activities in the communities to improve early presentation of cases to health facilities.