Resurgence of Ebola virus in 2021 in Guinea suggests a new paradigm for outbreaks.

Seven years after the declaration of the first epidemic of Ebola virus disease in Guinea, the country faced a new outbreak-between 14 February and 19 June 2021-near the epicentre of the previous epidemic1,2. Here we use next-generation sequencing to generate complete or near-complete genomes of Zaire ebolavirus from samples obtained from 12 different patients. These genomes form a well-supported phylogenetic cluster with genomes from the previous outbreak, which indicates that the new outbreak was not the result of a new spillover event from an animal reservoir. The 2021 lineage shows considerably lower divergence than would be expected during sustained human-to-human transmission, which suggests a persistent infection with reduced replication or a period of latency. The resurgence of Zaire ebolavirus from humans five years after the end of the previous outbreak of Ebola virus disease reinforces the need for long-term medical and social care for patients who survive the disease, to reduce the risk of re-emergence and to prevent further stigmatization.

Pharmacokinetics of Ribavirin in the Treatment of Lassa Fever: An Observational Clinical Study at the Irrua Specialist Teaching Hospital, Edo State, Nigeria.

BACKGROUND: Lassa fever is endemic in large parts of West Africa. The recommended antiviral treatment is ribavirin. Two treatment regimens are currently endorsed in Nigeria: the "McCormick regimen" based on a study published in 1986 and the "Irrua regimen" constituting a simplified schedule developed at the Irrua Specialist Teaching Hospital, Nigeria. Evidence for the safety and efficacy of ribavirin in Lassa fever patients is poor and pharmacokinetic data for both regimens are lacking. METHODS: Polymerase chain reaction-confirmed Lassa fever patients with mild to moderate disease severity were invited to participate in this prospective, observational pharmacokinetic study. Pharmacokinetics of ribavirin, clinical, virologic, and clinical laboratory parameters were assessed. RESULTS: Using a population pharmacokinetic approach, plasma concentrations of ribavirin were best described by a 3-compartment model. Drug exposure was remarkably consistent between participants. Overall, drug clearance was 28.5% lower in female compared with male participants. Median (5th-95th percentile) time above half maximal inhibitory concentration (IC50) was 37.3% (16.9%-73.1%), 16.7% (8.2%-58.5%), and 9.6% (4.9%-38.4%) on days 1, 7, and 8, respectively. Clinical laboratory parameters indicated reduction of cell damage and development of hemolytic anemia in the course of the treatment period. CONCLUSIONS: This observational study characterizes the pharmacokinetics of ribavirin in the treatment of Lassa fever indicating consistent exposure across patients. Whereas only a short time interval of concentrations above the IC50 implies rather low antiviral efficacy in vivo, the prominent reduction of cell damage markers might point to indirect-potentially anti-inflammatory-effects of ribavirin. The role of ribavirin in the treatment of Lassa fever requires further scrutiny.

Lassa Virus in Pygmy Mice, Benin, 2016-2017.

Lassa virus has been identified in 3 pygmy mice, Mus baoulei, in central Benin. The glycoprotein and nucleoprotein sequences cluster with the Togo strain. These mice may be a new reservoir for Lassa virus in Ghana, Togo, and Benin.

Virus Load Kinetics in Lassa Fever Patients Treated With Ribavirin: A Retrospective Cohort Study From Southern Nigeria.

Background: The standard of care for Lassa fever is the use of ribavirin with supportive therapy. There is little information on the course of viremia and its relationship with clinical outcomes in patients treated with ribavirin. Methods: We conducted a retrospective analysis of virologic and clinical parameters of 152 reverse transcription polymerase chain reaction-confirmed Lassa fever cases admitted and treated with ribavirin therapy. We describe the Lassa virus RNA kinetics in blood in relation to the clinical course of the patients. Results: The overall mortality was 9%. The median duration (interquartile range [IQR]) of illness before admission was 8 (5-12) days. Median (IQR) Ct values on admission (t0 ) were lower among patients who died (21 [20-27]) than in those who survived (34 [30-37]; P < .01). The receiver operating characteristics curve of the association between outcome and Ct value at t0 had a high classification performance, with an AUC of 0.92 (95% CI, 0.86-0.98). The median time to viral clearance (IQR) was 10 (5-15) days. The viral load decreased steadily with the duration of treatment, and all survivors achieved viral clearance within 25 days of hospitalization. Conclusions: Our study demonstrates that the Ct value on admission has prognostic value and Lassa fever patients treated with ribavirin typically clear the virus within 3-4 weeks of hospitalization. This kinetics has implications for the design of clinical case management and future clinical trial protocols.

Oxygen supply from the bird's eye perspective: globin E is a respiratory protein in the chicken retina.

The visual process in the vertebrate eye requires high amounts of metabolic energy and thus oxygen. Oxygen supply of the avian retina is a challenging task because birds have large eyes, thick retinae, and high metabolic rates but neither deep retinal nor superficial capillaries. Respiratory proteins such as myoglobin may enhance oxygen supply to certain tissues, and thus the mammalian retina harbors high amounts of neuroglobin. Globin E (GbE) was recently identified as an eye-specific globin of chicken (Gallus gallus). Orthologous GbE genes were found in zebra finch and turkey genomes but appear to be absent in non-avian vertebrate classes. Analyses of globin phylogeny and gene synteny showed an ancient origin of GbE but did not help to assign it to any specific globin type. We show that the photoreceptor cells of the chicken retina have a high level of GbE protein, which accumulates to ∼10 µM in the total eye. Quantitative real-time RT-PCR revealed an ∼50,000-fold higher level of GbE mRNA in the eye than in the brain. Spectroscopic analysis and ligand binding kinetics of recombinant chicken GbE reveal a penta-coordinated globin with an oxygen affinity of P(50) = 5.8 torrs at 25 °C and 15 torrs at 41 °C. Together these data suggest that GbE helps to sustain oxygen supply to the avian retina.

Virus persistence after recovery from acute Lassa fever in Nigeria: a 2-year interim analysis of a prospective longitudinal cohort study.

BACKGROUND: There is anecdotal evidence for Lassa virus persistence in body fluids. We aimed to investigate various body fluids after recovery from acute Lassa fever, describe the dynamics of Lassa virus RNA load in seminal fluid, and assess the infectivity of seminal fluid. METHODS: In this prospective, longitudinal, cohort study we collected plasma, urine, saliva, lacrimal fluid, vaginal fluid, and seminal fluid from Lassa fever survivors from Irrua Specialist Teaching Hospital in Edo State, Nigeria. Inclusion criteria for participants were RT-PCR-confirmed Lassa fever diagnosis and age 18 years or older. Samples were taken at discharge from hospital (month 0) and at months 0·5, 1, 3, 6, 9, 12, 18, and 24 after discharge. The primary objective of this study was to quantitatively describe virus persistence and clearance and assess the infectivity of seminal fluid. Lassa virus RNA was detected using real-time RT-PCR. Infectivity was tested in cell culture and immunosuppressed mice. We used a linear mixed-effect model to analyse the dynamics of virus persistence in seminal fluid over time. FINDINGS: Between Jan 31, 2018, and Dec 11, 2019, 165 participants were enrolled in the study, of whom 159 were eligible for analysis (49 women and 110 men). Low amounts of Lassa virus RNA were detected at month 0 in plasma (49 [45%] of 110 participants), urine (37 [34%]), saliva (five [5%]), lacrimal fluid (ten [9%]), and vaginal fluid (seven [21%] of 33 female participants). Virus RNA was cleared from these body fluids by month 3. However, 35 (80%) of 44 male participants had viral RNA in seminal fluid at month 0 with a median cycle threshold of 26·5. Lassa virus RNA remained detectable up to month 12 in seminal fluid. Biostatistical modelling estimated a clearance rate of 1·19 log10 viral RNA copies per month and predicted that 50% of male survivors remain Lassa virus RNA-positive in seminal fluid for 83 days after hospital discharge and 10% remain positive in seminal fluid for 193 days after discharge. Viral RNA persistence in seminal fluid for 3 months or more was associated with higher viraemia (p=0·006), more severe disease (p=0·0075), and longer hospitalisation during the acute phase of Lassa fever (p=0·0014). Infectious virus was isolated from 48 (52%) of 93 virus RNA-positive seminal fluid samples collected between month 0 and 12. INTERPRETATION: Lassa virus RNA is shed in various body fluids after recovery from acute disease. The persistence of infectious virus in seminal fluid implies a risk of sexual transmission of Lassa fever. FUNDING: German Federal Ministry of Health, German Research Foundation, Leibniz Association.

Validation of Inactivation Methods for Arenaviruses.

Several of the human-pathogenic arenaviruses cause hemorrhagic fever and have to be handled under biosafety level 4 conditions, including Lassa virus. Rapid and safe inactivation of specimens containing these viruses is fundamental to enable downstream processing for diagnostics or research under lower biosafety conditions. We established a protocol to test the efficacy of inactivation methods using the low-pathogenic Morogoro arenavirus as surrogate for the related highly pathogenic viruses. As the validation of chemical inactivation methods in cell culture systems is difficult due to cell toxicity of commonly used chemicals, we employed filter devices to remove the chemical and concentrate the virus after inactivation and before inoculation into cell culture. Viral replication in the cells was monitored over 4 weeks by using indirect immunofluorescence and immunofocus assay. The performance of the protocol was verified using published inactivation methods including chemicals and heat. Ten additional methods to inactivate virus in infected cells or cell culture supernatant were validated and shown to reduce virus titers to undetectable levels. In summary, we provide a robust protocol for the validation of chemical and physical inactivation of arenaviruses in cell culture, which can be readily adapted to different inactivation methods and specimen matrices.