Factors Associated with Lassa fever Mortalities in Ondo State Nigeria

Abstract

Background: Lassa fever is a viral hemorrhagic disease that is endemic in at least nine countries in West Africa. The virus causes significant morbidity and mortality, especially in the endemic region. Several studies have been conducted on epidemiological drivers and clinical management of Lassa fever cases; however, extremely few studies focused on factors responsible for Lassa fever mortalities. This study describes epidemiological and clinical factors that are associated with Lassa fever deaths in Ondo State, Nigeria. Ondo State is one of the hotspot states which has been recording extremely high mortality rates in recent years, hence it is crucial to identify factors associated with increased mortality to provide valuable insights for public health emergency managers to tailor effective outbreak response interventions that could improve case outcomes and reduce Lassa fever mortality. Objectives: The general objective of the study is to evaluate factors associated with Lassa fever deaths in Ondo State, Nigeria, and to determine case fatality rates and epidemiological and clinical characteristics of Lassa fever deaths recorded in Ondo State over four years between 2018 and 2021. Methods: Secondary data on Lassa fever cases and deaths recorded in Ondo State between 2018 to 2021 were obtained from Nigeria’s national Surveillance system. The data were retrospectively analyzed, and case fatality rates were determined. The Association between clinical and epidemiological factors and the outcome of confirmed Lassa fever cases were evaluated. Result: During the study period, a total of 1028 cases were laboratory confirmed out of which 233 died CFR 22.7%. The highest CFR at 28.2% was recorded in 2021 while the lowest CFR at 19.3% was recorded in 2018. Of the total cases, 538 (50.7%) confirmed cases are males while 490 (49.3%) are female. About 53.4% of all cases are adults between 26–59 years while children aged five and below totaled 49 representing 4.8%. Urban dwellers accounted for 83% of all cases while only 16.8% of cases were reported from rural areas. However, a higher CFR of 28.3% (49/173) was recorded among rural dwellers than among those residing in urban centers. The most common clinical features of symptomatic cases among patients with laboratory-confirmed Lassa fever were fever 863(83.9), fatigue 584 (56.8%), headache 515 (50.1%), abdominal pain 388 (37.3) and cough 331 (32.2%). Mortalities among confirmed cases that also had cough is highest at CFR 26.3 (87/331) followed by those with abdominal pain at CFR 23.2 (90/388). Confirmed cases that had a fever as a symptom had a 21.8% CFR (188/863) those with headaches had a CFR of 19.8% (102/515), and those with fatigue has a CFR of 18.5%. The odds of fatal outcomes for patients that are positive for Lassa fever and present with symptoms of fatigue remain significant even after adjusting for age, sex, education, and occupation. Moreover, the odds of death from Lassa fever remain significant for adults aged 60 and above after controlling for symptoms, sex, education, and occupation. Conclusion: This study observed a steady increase in case fatality rates among confirmed Lassa fever cases in Ondo State. Health authorities in the State need to critically review health system factors to ensure rapid case detection and access to quality case management for all confirmed Lassa fever cases in the State. Lassa fever is more fatal among adults aged 60 and above and more deaths were recorded among less educated individuals in the study population. Targeted risk communication messages and radio/TV jingles in local languages should be tailored to address this segment of society with preventive messaging and good health-seeking behavior. Symptomatic cases should quickly be brought under the care and close attention should be paid to patients that are 60 years and above and those who presented with fatigue as they are more likely to die from Lassa fever infection.