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. Sixty-nine (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.

Development of an RT-LAMP assay for the detection of Lassa viruses in southeast and south-central Nigeria

Lassa virus (LASV) causes Lassa fever (LF), a viral hemorrhagic fever endemic in West Africa. LASV strains are clustered into six lineages according to their geographic location. To confirm a diagnosis of LF, a laboratory test is required. Here, a reverse transcription loop-mediated isothermal amplification (RT-LAMP) assay using a portable device for the detection of LASV in southeast and south-central Nigeria using three primer sets specific for strains clustered in lineage II was developed. The assay detected in vitro transcribed LASV RNAs within 23 min and was further evaluated for detection in 73 plasma collected from suspected LF patients admitted into two health settings in southern Nigeria. The clinical evaluation using the conventional RT-PCR as the reference test revealed a sensitivity of 50% in general with 100% for samples with a viral titer of 9500 genome equivalent copies (geq)/mL and higher. The detection limit was estimated to be 4214 geq/mL. The assay showed 98% specificity with no cross-reactivity to other viruses which cause similar symptoms. These results suggest that this RT-LAMP assay is a useful molecular diagnostic test for LF during the acute phase, contributing to early patient management, while using a convenient device for field deployment and in resource-poor settings.