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Summary 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.

The name arenavirus comes from the Latin arenosus (sandy). Ribosomes are packaged within arenavirus virions and these are responsible for the “sandy” appearance of the particles. Arenavirus virions are enveloped with helical nucleocapsids and are pleomorphic, ranging in size from 100 to 130 nm in diameter. Structural proteins include a nucleocapsid protein (N), a matrix-like protein (Z), and two glycoproteins derived from a single precursor. Arenaviruses are segmented RNA viruses that replicate using an overall strategy common to negative-strand RNA viruses. However, both genome segments (large (L) and small (S)) are ambisense in their coding strategy. Rodents are natural hosts of many arenaviruses though some can infect humans through contact with infected rodents or inhalation of infectious urine or feces.

We conducted a survey for group-specific indirect immunofluorescence antibody to mammarenaviruses by using Lassa fever and Mopeia virus antigens on serum specimens of 5,363 rodents of 33 species collected in South Africa and Zimbabwe during 1964–1994. Rodents were collected for unrelated purposes or for this study and stored at −70°C. We found antibody to be widely distributed in the 2 countries; antibody was detected in serum specimens of 1.2%–31.8% of 14 species of myomorph rodents, whereas 19 mammarenavirus isolates were obtained from serum specimens and viscera of 4 seropositive species. Phylogenetic analysis on the basis of partial nucleoprotein sequences indicates that 14 isolates from Mastomys natalensis, the Natal multimammate mouse, were Mopeia virus, whereas Merino Walk virus was characterized as a novel virus in a separate study. The remaining 4 isolates from 3 rodent species potentially constitute novel viruses pending full characterization.

Lassa fever is a longstanding public health concern in West Africa. Recent molecular studies have confirmed the fundamental role of the rodent host (Mastomys natalensis) in driving human infections, but control and prevention efforts remain hampered by a limited baseline understanding of the disease’s true incidence, geographical distribution and underlying drivers. Here, we show that Lassa fever occurrence and incidence is influenced by climate, poverty, agriculture and urbanisation factors. However, heterogeneous reporting processes and diagnostic laboratory access also appear to be important drivers of the patchy distribution of observed disease incidence. Using spatiotemporal predictive models we show that including climatic variability added retrospective predictive value over a baseline model (11% decrease in out-of-sample predictive error). However, predictions for 2020 show that a climate-driven model performs similarly overall to the baseline model. Overall, with ongoing improvements in surveillance there may be potential for forecasting Lassa fever incidence to inform health planning., Lassa Fever is a rodent-borne viral haemorrhagic fever that is a public health problem in West Africa. Here, the authors develop a spatiotemporal model of the socioecological drivers of disease using surveillance data from Nigeria, and find evidence of climate sensitivity.

Vaccinia virus has been used as a smallpox vaccine. Now that smallpox has been eradicated, the vaccinia virus is expected to be used as a bioterrorism countermeasure and a recombinant vaccine vector for other infectious diseases, such as viral hemorrhagic fevers. Many vaccinia virus strains were used as smallpox vaccines in the smallpox eradication campaign coordinated by the World Health Organization. These strains can be classified into generations, according to the history of improving production methods and efforts to reduce the adverse reactions. Significantly, the third-generation of smallpox vaccine strains, which include modified vaccinia Ankara (MVA) and LC16m8, are currently popular as recombinant vaccine vectors due to their well-balanced safety and immunogenicity profiles. The present review firstly focuses on the characteristics of the smallpox vaccine generations. The historical background of the development of the third-generation smallpox vaccine strains is detailed, along with the history of the transition of the vaccinia virus generation used as vectors for hemorrhagic fever vaccines to the third generation. Among the vaccinia viruses, MVA is currently the most commonly used vector for developing hemorrhagic fever vaccines, including dengue fever, yellow fever, Ebola viral disease, Lassa fever, Rift Valley fever, and Crimean-Congo hemorrhagic fever. LC16m8 is a vaccine candidate for severe fever with thrombocytopenia syndrome. The current status and recent advances in the development of these hemorrhagic fever vaccines using third-generation vaccinia strains are discussed.

Background: The current resurgence and transmission dynamics of Lassa fever (LF) within an endemic community in Nigeria calls for concern. Lassa fever virus is known to be transmitted from rodents to humans as well as from human to human. This study aims to compare the knowledge, attitude/practices and prevention of Community dwellers (CD) and Contacts of confirmed Lassa fever patients (CCP) with respect to LF in an endemic area in Nigeria. Methodology: This is a comparative cross-sectional study conducted between 2018 and 2019 during an outbreak of LF disease in Ondo State, Nigeria. A total of 250 consenting CD and 104 CCP were randomly selected to participate in this study. They were administered semi-structured questionnaires which were analysed using SPSSv23. Lassa fever disease causative agents, mode of transmission and prevention as well as actions on response to Lassa virus infections were assessed among respondents. Data were analysed and presented using descriptive statistics at 95% confidence interval and (p

Background: The prevention and control of Lassa fever depends on the adoption of appropriate behavioural practices. The expected changes are best explained using the Health Belief Model. The study investigated respondents’ perception of their risk for Lassa fever infection and its associated factors in Akhalowa community of Edo State. Methods: This cross-sectional study was conducted among eligible heads of households using a structured interviewer-administered questionnaire. Data were analyzed using descriptive and inferential statistics on IBM SPSS version 22.0. A p-value < 0.05 at 95% confidence interval was considered statistically significant. Results: The participants included 220 respondents with mean age (SD) of 37.9 (13.2) years. There were 127 (57.7%) females and 143 (65.0%) respondents had at least secondary education. One hundred and ninety one (86.8%) of them were aware of Lassa fever, out of which 146 (76.4%) had overall good perception of their risk for the disease and 144 (75.4%) agreed that Lassa fever was a problem in the community. One hundred and seventy seven (92.7%) agreed that complying with preventive measures would protect them against Lassa fever. Respondents’ good knowledge of Lassa fever was the only significant predictor of good perception of risk for Lassa fever [Odds Ratio=3.806; 95 CI = 1.498-9.672, p=0.005]. Conclusion: The study revealed overall good perception of risk for Lassa fever among the respondents. It is therefore recommended that this is sustained through continuous risk communication messages on the prevention and control of Lassa fever to the people by the Edo State and local governments.

Lassa fever, caused by the Lassa virus of the Arenaviruses family, is a re-emerging public health concern that has led to 300,000 infections and 5000 deaths annually in Africa. Highly prevalent in Sierra Leone, Liberia, Guinea, Nigeria, Côte d'lvoire, Ghana, Togo, and Benin, patients infected with the virus can manifest with cough, sore throat, headache, nausea, and vomiting among other symptoms. Coexisting with the coronavirus disease 2019 (COVID-19) pandemic and its impacts, cases of Lassa fever in the African population have been reported to decrease due to hesitancy in visiting clinics that leads to unreported cases-all contributing to a silent outbreak in West Africa. Thus, to overcome current burdens, gaps, and challenges caused by Lassa fever amidst COVID-19 in Africa, various recommendations for efficient control of transmission, measures for disease containment, and strategies to correct misperceptions were made.

Nigeria Centres for Disease Control and Prevention established an event-based surveillance (EBS) system in 2016 to supplement traditional surveillance structures. The EBS system is comprised of an internet-based data mining tool and a call center. To evaluate the EBS system for usefulness, simplicity, acceptability, timeliness, and data quality, we performed a descriptive analysis of signals received during September 2017-June 2018. We used questionnaires, semistructured interviews, and direct observation to collect information from EBS staff. Amongst 43,631 raw signals detected, 138 (0.3%) were escalated; 63 (46%) of those were verified as events, including 25 Lassa fever outbreaks and 13 cholera outbreaks. Interviewees provided multiple examples of earlier outbreak detections but suggested notifications and logging could be improved to ensure action. EBS proved effective in detecting outbreaks, but we noted clear opportunities for efficiency gains. We recommend improving signal logging, standardizing processes, and revising outputs to ensure appropriate public health action.

Lassa fever remains endemic in parts of West Africa and continues to pose as a quiescent threat globally. We described the background on Lassa fever, factors contributing to its emergence and spread, preventive measures, and potential solutions. This review provides a holistic and comprehensive source for academicians, clinicians, researchers, policymakers, infectious disease epidemiologists, virologists, and other stakeholders.

Lack of experimental human models hinders research on Lassa hemorrhagic fever and the development of treatment strategies. Here, we report the first chip‐based model for Lassa hemorrhagic syndrome. The chip features a microvessel interfacing collagen network as a simple mimic for extracellular matrix, allowing for quantitative and real‐time vascular integrity assessment. Luminal infusion of Lassa virus‐like particles led to a dramatic increase in vascular permeability in a viral load‐dependent manner. Using this platform, we showed that Fibrin‐derived peptide FX06 can be used to suppress the vascular integrity loss. This simple chip‐based model proved promising in the assessment of disease severity and provides an easy‐to‐use platform for future investigation of Lassa pathogenesis and drug development in a human‐like setting., An organ‐on‐a‐chip model that imitates Lassa hemorrhagic shock syndrome was developed and used to test drug candidate. The chip is composed of a microvessel interfacing collagen network as a simple mimic for extracellular matrix, which can recapitulate the physiological barrier function of a natural vessel and luminal infusion of Lassa virus‐like particles led to a dramatic increase in vascular permeability. Using this platform, a potential drug, Fibrin‐derived peptide FX06, shows its ability to suppress the Lassa‐induced vascular integrity loss.

Diseases caused by many highly pathogenic viruses, including Ebola virus (EBOV) and Lassa virus (LASV), present with nonspecific signs and symptoms that overlap with common tropical diseases such as malaria. Initial diagnostic tests performed on patients under investigation for viral hemorrhagic fevers routinely include analysis of peripheral blood smears to detect and quantify Plasmodium species. In light of recent and ongoing Ebola virus disease and Lassa fever epidemics, clinical laboratories around the world require protocols for dealing with highly infectious specimens from patients with suspected or confirmed high-consequence diseases. Few validated protocols for safe analysis of peripheral blood smears are available, revealing a need for further research. In this study, we evaluated the performance of two plastic microscope slide types that offer safe alternatives to glass slides, determined the temporal parameters required to inactivate EBOV and LASV in thin blood smears by methanol fixation, and assessed the virucidal activity of Giemsa stain. Both types of plastic microscope slides performed optimally; there were no significant differences in blood cell morphology or tinctorial properties nor were differences noted in Plasmodium ovale morphology or staining, when compared with glass slides. For both EBOV and LASV, viable viruses were not detected in thin blood smears following fixation in absolute methanol for at least 2 minutes. By contrast, viable EBOV and LASV were recovered from all Giemsa-stained thick blood smears.

Lassa fever (LF) causes multisystem disease and has a fatality rate

Ribavirin is another nucleotide analogue with a wide range of antiviral efficacy against multiple viruses, including respiratory syncytial virus, influenza virus, measles, herpes simplex virus, human immunodeficiency virus, Lassa fever, and hepatitis B and C viral infections. Ribavirin can indeed be delivered orally, intravenous infusion or via a nebulizer. This survey was initiated to study the awareness of ribavirin therapy amongst dental students. This was cross-sectional type research done with a questionnaire distributed among 100 dental college students in Chennai. A self-designed questionnaire with 10 items that elicit knowledge and understanding of ribavirin therapy amongst dental college students. Questionnaires were circulated through an online website survey planet. The questions explored the awareness of Ribavirin therapy, indications, contra indications, mechanism of action and side effects. After the responses were received from 100 participants, data were collected and analysed. 7% were aware of Ribavirin therapy. 5% were aware of the mechanism of action of Ribavirin therapy. 5% were aware of the indications of Ribavirin therapy .3% were aware of the contraindications of Ribavirin therapy .4%. were aware of about adverse effects of Ribavirin therapy. The awareness about ribavirin in managing viral infections was less among dental students. Increased awareness and educational programs should be initiated to spread knowledge about ribavirin therapy.

Arenaviruses, such as Lassa virus (LASV), can cause severe and fatal hemorrhagic fevers (e.g., Lassa fever, LF) in humans with no vaccines or therapeutics. Research on arenavirus-induced hemorrhagic fevers (AHFs) has been hampered by the highly virulent nature of these viral pathogens, which require high biocontainment laboratory, and the lack of an immune-competent small animal model that can recapitulate AHF disease and pathological features. Guinea pig infected with Pichinde virus (PICV), an arenavirus that does not cause disease in humans, has been established as a convenient surrogate animal model for AHFs as it can be handled in a conventional laboratory. The PICV strain P18, derived from sequential passaging of the virus 18 times in strain 13 inbred guinea pigs, causes severe febrile illness in guinea pigs that is reminiscent of lethal LF in humans. As inbred guinea pigs are not readily available and are difficult to maintain, outbred Hartley guinea pigs have been used but they show a high degree of disease heterogeneity upon virulent P18 PICV infection. Here, we describe an improved outbred guinea-pig infection model using recombinant rP18 PICV generated by reverse genetics technique followed by plaque purification, which consistently shows >90% mortality and virulent infection. Comprehensive virological, histopathological, and immunohistochemical analyses of the rP18-virus infected animals show similar features of human LASV infection. Our data demonstrate that this improved animal model can serve as a safe, affordable, and convenient surrogate small animal model for studying human LF pathogenesis and for evaluating efficacy of preventative or therapeutic approaches.

Lassa fever is a disease that is not well-known worldwide, particularly due to the inability of the multimammate rat, the primary vector of the Lassa virus, to breed in temperate regions. The aim of this review is to provide an overview of the disease and its modus operandi while also providing information about trends in the past decade, as well as proven strategies that have been used to manage its spread.

Frequent outbreaks of the Lassa virus had been reported weekly in Nigeria in recent months by the Nigerian Centre for Disease Control, where 23 of the 36 states in the country recorded confirmed cases in 2019 with a fatality of 20 6% The present research assesses the knowledge and risk factors associated with continuous outbreaks of Lassa fever in Nigeria using the inhabitants of some endemic communities in Edo state as a case study The research was conducted using a 25-item self-administered semi-structured questionnaire to elicit responses from individuals in some Lassa fever endemic communities on basic information about the biology, epidemiology, prevention and control of the disease Data analysis was done using the Statistical Package for Social Sciences (SPSS) Version 23 0 Overall, 122 (43 7%) of the 279 participants had good knowledge of the Lassa virus, 78 (28 0%) had fair knowledge while 79 (28 3%) had poor knowledge Furthermore, 148 (53 0%) of the respondents knew that Lassa fever is caused by a virus while 260 (93 2%) knew that rats are the vector for the virus Only 72 (25 8%) of participants knew the effective methods of food storage to avoid vector contact and contamination with the virus Survey showed that there is still a dearth of knowledge and awareness of the risk factors associated with frequent outbreaks of the Lassa virus in endemic communities There is need to intensify efforts on public health education and community mobilization to curtail future outbreaks of the disease

Lassa virus (LASV) is the causative agent of Lassa fever (LF), an often-fatal hemorrhagic disease. LF is endemic in Nigeria, Sierra Leone and other West African countries. Diagnosis of LASV infection is challenged by the genetic diversity of the virus, which is greatest in Nigeria. The ReLASV Pan-Lassa Antigen Rapid Test (Pan-Lassa RDT) is a point-of-care, in vitro diagnostic test that utilizes a mixture of polyclonal antibodies raised against recombinant nucleoproteins of representative strains from the three most prevalent LASV lineages (II, III and IV). We compared the performance of the Pan-LASV RDT to available quantitative PCR (qPCR) assays during the 2018 LF outbreak in Nigeria. For patients with acute LF (RDT positive, IgG/IgM negative) during initial screening, RDT performance was 83.3% sensitivity and 92.8% specificity when compared to composite results of two qPCR assays. 100% of samples that gave Ct values below 22 on both qPCR assays were positive on the Pan-Lassa RDT. There were significantly elevated case fatality rates and elevated liver transaminase levels in subjects whose samples were RDT positive compared to RDT negative.

At the time of writing in 2019, there have been 754 confirmed cases of Lassa fever in Nigeria, 21% of whom have died. Lassa is on the priority pathogen list for WHO’s R&D Blueprint for Action to Prevent Epidemics. In September 2019, WHO convened 67 scientists, regulators, ethicists, public health officials, funders and vaccine developers to discuss the end-to-end clinical development plan for Lassa fever vaccines. The substantial increases in vaccine trial capacity in Africa were reviewed, together with lessons learned from the evaluation of vaccines against HIV, TB, malaria, and Ebola in Africa. Participants agreed on a pathway for Lassa vaccine trial progression, as outlined in WHO’s Lassa fever R&D roadmap and the WHO Lassa fever Target Product Profile. Two Phase 1 trials of Lassa vaccines have already started, and it was agreed that continuing interactions between high income and African regulatory and ethics authorities and WHO will be important in progression towards Phase 2b/3 efficacy trials in Lassa fever endemic areas. There was agreement that, for diseases whose burden is mainly in Africa, it should be the norm that African regulatory authorities are consulted on trial design/progression before first-in-human Phase 1 trials. Phase 2b-3 vaccine trial capacity needs to be in place in high Lassa fever burden areas where efficacy trials will take place. Licensure of one or more Lassa fever vaccines suitable for West African populations is a realistic goal in the next 5 years, with CEPI and WHO aligned on the pathway forward for vaccine development.

Lassa fever is an animal-borne acute viral illness caused by the Lassa virus. This disease is endemic in parts of West Africa including Benin, Ghana, Guinea, Liberia, Mali, Sierra Leone, and Nigeria. We formulate a mathematical model for Lassa fever disease transmission under the assumption of a homogeneously mixed population. We highlighted the basic factors influencing the transmission of Lassa fever and also determined and analyzed the important mathematical features of the model. We extended the model by introducing various control intervention measures, like external protection, isolation, treatment, and rodent control. The extended model was analyzed and compared with the basic model by appropriate qualitative analysis and numerical simulation approach. We invoked the optimal control theory so as to determine how to reduce the spread of the disease with minimum cost.