Early onset of neurological features differentiates two outbreaks of Lassa fever in Ebonyi state, Nigeria during 2017–2018.

Lassa fever (LF) is an acute viral haemorrhagic illness with various non-specific clinical manifestations. Neurological symptoms are rare at the early stage of the disease, but may be seen in late stages, in severely ill patients.The aim of this study was to describe the epidemiological evolution, socio-demographic profiles, clinical characteristics, and outcomes of patients seen during two Lassa fever outbreaks in Ebonyi State, between December 2017 and December 2018. Routinely collected clinical data from all patients admitted to the Virology Centre of the hospital during the period were analysed retrospectively.Out of a total of 83 cases, 70(84.3%) were RT-PCR confirmed while 13(15.7%) were probable cases. Sixtynine(83.1%) patients were seen in outbreak 1 of whom 53.6% were urban residents, while 19%, 15%, and 10% were farmers, students and health workers respectively. There were 14(16.8%)patients, seen in second outbreak with 92.9% rural residents. There were differences in clinical symptoms, signs and laboratory findings between the two outbreaks. The case fatality rates were 29.9% in outbreak 1 and 85.7% for outbreak 2. Neurological features and abnormal laboratory test results were associated with higher mortality rate, seen in outbreak 2. This study revealed significant differences between the two outbreaks. Of particular concern was the higher case fatality during the outbreak 2 which may be from a more virulent strain of the Lassa virus. This has important public health implications and further molecular studies are needed to better define its characteristics. Author summary: Neurological manifestations are uncommon in the early stages of Lassa Fever. In Ebonyi State, an unusual pattern was observed between two outbreaks that occurred quite close together in time but with distinctly different presentations. Previous studies on the 2018 outbreak focused on the first part of the outbreak between December 2017—May 2018. We therefore compared the two outbreaks and observed that patients in the second outbreak which occurred between August 2018-December 2018, presented with early neurological symptoms and a high mortality rate. This observation highlights the need for further evaluation and molecular studies. [ABSTRACT FROM AUTHOR]