A review of the recent advances on Lassa fever with special reference to molecular epidemiology and progress in vaccine development

Lassa fever, a viral hemorrhagic fever caused by the Lassa virus (LASV), is endemic in West Africa and is associated with high morbidity and mortality. At least three of the four proposed seven lineages of LASV are found in Nigeria, where the multimammate rat, Mastomys natalensis, serves as the primary reservoir. Endemic countries report approximately 200,000 infections and 5,000 deaths annually, with Nigeria experiencing thousands of infections and hundreds of deaths including healthcare workers. The aim of this review is to provide scientific information for better understanding of the evolutionary biology, molecular epidemiology, pathogenesis, diagnosis, and prevention of Lassa fever in Nigeria and other endemic regions worldwide, which can lead to improved control efforts and reduce morbidity and mortality from recurrent epidemics. To achieve this aim, observational studies such as case series, cross-sectional and cohort studies published between December 2017 and September 2022 were searched for on various online databases including Google Scholar, Africa Journals Online (AJOL), Research Gates, PubMed, PMIC, NCDC, and WHO websites. Although the origin and evolutionary history, and the transmission dynamics of Lassa virus have been revealed through recent. molecular epidemiological studies, the factors that drive the evolution of the virus remain unclear. Genetic changes in the viral genome may have enabled the virus to adapt to humans. Diagnosis of Lassa fever has also advanced from basic serological tests to more sophisticated methods such as quantitative real time polymerase chain reaction (qRT-PCR) and sequencing, which are particularly useful for identifying outbreak strains. Several vaccines, including recombinant vesicular stomatitis virus (rVSV), virus-like particle (VLP), and DNA-based vaccines, have shown promise in animal models and some have progressed to phase 2 clinical trials. Preventing and controlling Lassa fever is critical to safeguard the health and well-being of affected communities. Effective measures such as rodent control, improved sanitation, and early detection and isolation of infected individuals are essential for reducing transmission. Ongoing research into the genetic and ecological factors that drive the evolution of Lassa virus is necessary to reduce the impacts of Lassa fever.

Ebola outbreak in Guinea, 2021: Clinical care of patients with Ebola virus disease

Background: Experience from the Zaire Ebolavirus epidemic in the eastern Democratic Republic of the Congo (2018­2020) demonstrates that early initiation of essential critical care and administration of Zaire Ebolavirus specific monoclonal antibodies may be associated with improved outcomes among patients with Ebola virus disease (EVD). Objectives: This series describes 13 EVD patients and 276 patients with suspected EVD treated during a Zaire Ebolavirus outbreak in Guinea in 2021. Method: Patients with confirmed or suspected EVD were treated in two Ebola treatment centres (ETC) in the region of N'zérékoré. Data were reviewed from all patients with suspected or confirmed EVD hospitalised in these two ETCs during the outbreak (14 February 2021 ­ 19 June 2021). Ebola-specific monoclonal antibodies, were available 2 weeks after onset of the outbreak. Results: Nine of the 13 EVD patients (age range: 22­70 years) survived. The four EVD patients who died, including one pregnant woman, presented with multi-organ dysfunction and died within 48 h of admission. All eight patients who received Ebola-specific monoclonal antibodies survived. Four of the 13 EVD patients were health workers. Improvement of ETC design facilitated implementation of WHO-recommended 'optimized supportive care for EVD'. In this context, pragmatic clinical training was integrated in routine ETC activities. Initial clinical manifestations of 13 confirmed EVD patients were similar to those of 276 patients with suspected, but subsequently non confirmed EVD. These patients suffered from other acute infections (e.g. malaria in 183 of 276 patients; 66%). Five of the 276 patients with suspected EVD died. One of these five patients had Lassa virus disease and a coronavirus disease 2019 (COVID-19) co-infection. Conclusion: Multidisciplinary outbreak response teams can rapidly optimise ETC design. Trained clinical teams can provide WHO-recommended optimised supportive care, including safe administration of Ebola-specific monoclonal antibodies. Pragmatic training in essential critical care can be integrated in routine ETC activities. Contribution: This article describes clinical realities associated with implementation of WHO-recommended standards of 'optimized supportive care' and administration of Ebola virus specific treatments. In this context, the importance of essential design principles of ETCs is underlined, which allow continuous visual contact and verbal interaction of health workers and families with their patients. Elements that may contribute to further quality of care improvements for patients with confirmed or suspected EVD are discussed.

A review of the recent advances on Lassa fever with special reference to molecular epidemiology and progress in vaccine development

Lassa fever, a viral hemorrhagic fever caused by the Lassa virus (LASV), is endemic in West Africa and is associated with high morbidity and mortality. At least three of the four proposed seven lineages of LASV are found in Nigeria, where the multimammate rat, Mastomys natalensis, serves as the primary reservoir. Endemic countries report approximately 200,000 infections and 5,000 deaths annually, with Nigeria experiencing thousands of infections and hundreds of deaths including healthcare workers. The aim of this review is to provide scientific information for better understanding of the evolutionary biology, molecular epidemiology, pathogenesis, diagnosis, and prevention of Lassa fever in Nigeria and other endemic regions worldwide, which can lead to improved control efforts and reduce morbidity and mortality from recurrent epidemics. To achieve this aim, observational studies such as case series, cross-sectional and cohort studies published between December 2017 and September 2022 were searched for on various online databases including Google Scholar, Africa Journals Online (AJOL), Research Gates, PubMed, PMIC, NCDC, and WHO websites. Although the origin and evolutionary history, and the transmission dynamics of Lassa virus have been revealed through recent molecular epidemiological studies, the factors that drive the evolution of the virus remain unclear. Genetic changes in the viral genome may have enabled the virus to adapt to humans. Diagnosis of Lassa fever has also advanced from basic serological tests to more sophisticated methods such as quantitative real time polymerase chain reaction (qRT-PCR) and sequencing, which are particularly useful for identifying outbreak strains. Several vaccines, including recombinant vesicular stomatitis virus (rVSV), virus-like particle (VLP), and DNA-based vaccines, have shown promise in animal models and some have progressed to phase 2 clinical trials. Preventing and controlling Lassa fever is critical to safeguard the health and well-being of affected communities. Effective measures such as rodent control, improved sanitation, and early detection and isolation of infected individuals are essential for reducing transmission. Ongoing research into the genetic and ecological factors that drive the evolution of Lassa virus is necessary to reduce the impacts of Lassa fever

La fièvre de Lassa, une fièvre hémorragique virale causée par le virus de Lassa (LASV), est endémique en Afrique de l'Ouest et est associée à une morbidité et une mortalité élevées. Au moins trois des quatre lignées proposées de LASV se trouvent au Nigeria, où le rat multimammaire, Mastomys natalensis, sert de réservoir principal. Les pays endémiques signalent environ 200,000 infections et 5,000 décès par an, le Nigéria connaissant des milliers d'infections et des centaines de décès, y compris des travailleurs de la santé. L'objectif de cette revue est de fournir des informations scientifiques pour une meilleure compréhension de la biologie évolutive, de l'épidémiologie moléculaire, de la pathogenèse, du diagnostic et de la prévention de la fièvre de Lassa au Nigeria et dans d'autres régions endémiques du monde, ce qui peut conduire à des efforts de contrôle améliorés et réduire la morbidité et la mortalité des épidémies récurrentes. Pour atteindre cet objectif, des études observationnelles telles que des séries de cas, des études transversales et de cohorte publiées entre décembre 2017 et septembre 2022 ont été recherchées sur diverses bases de données en ligne, notamment Google Scholar, Africa Journals Online (AJOL), Research Gate, PubMed, PMIC, Sites Web du NCDC et de l'OMS. Bien que l'origine et l'histoire évolutive, ainsi que la dynamique de transmission du virus de Lassa aient été révélées par des études épidémiologiques moléculaires récentes, les facteurs qui déterminent l'évolution du virus restent flous. Des modifications génétiques du génome viral pourraient avoir permis au virus de s'adapter à l'homme. Le diagnostic de la fièvre de Lassa est également passé des tests sérologiques de base à des méthodes plus sophistiquées telles que la réaction quantitative en chaîne par polymérase en temps réel (qRTPCR) et le séquençage, qui sont particulièrement utiles pour identifier les souches épidémiques. Plusieurs vaccins, y compris le virus recombinant de la stomatite vésiculeuse (rVSV), les particules pseudo-virales (VLP) et les vaccins à base d'ADN, se sont révélés prometteurs dans des modèles animaux et certains ont progressé vers des essais cliniques de phase 2. La prévention et le contrôle de la fièvre de Lassa sont essentiels pour préserver la santé et le bien-être des communautés touchées. Des mesures efficaces telles que le contrôle des rongeurs, l'amélioration de l'assainissement et la détection et l'isolement précoces des personnes infectées sont essentielles pour réduire la transmission. Des recherches continues sur les facteurs génétiques et écologiques qui déterminent l'évolution du virus de Lassa sont nécessaires pour réduire les impacts de la fièvre de Lassa.

Lassa fever coinfection with COVID-19 among health care workers: report of two cases

Lassa fever (LF) coinfection with hepatitis B and HIV has been reported among hospitalized patients in Southwest Nigeria and HIV patients coinfected with COVID-19 have been described among hospitalized patients in North Central Nigeria, no study has reported cases of coinfection of Lassa disease and COVID-19 among health care workers (HCWs) worldwide. A case report of two HCWs who were infected with both LF virus and SARS-CoV-2 virus at same time and were successfully managed without any sequelae. Both cases presented with typical signs of LF with COVID-19 suspected, they were promptly diagnosezd with positive outcomes after treatment. While case 1 became negative for LF virus and SARS-CoV-2 after 6 and 30 days, respectively, case 2 became negative for both viruses after 14 and 32 days, respectively. The diagnosis of LF-COVID-19 coinfection in HCWs is a frightening dimension to the health risks faced by HCWs, therefore, HCWs now more than ever before want to know what comes next and how safe is the practice of medicine

Knowledge, attitude and practice of infection prevention and control among healthcare workers: one year after an outbreak of nosocomial Lassa fever in a tertiary hospital in southeast Nigeria

Background: With the rise in cases of Lassa fever in recent times in West Africa, the healthcare setting continues to pose significant risk especially among healthcare workers (HCWs) for diseases like Lassa fever that are transmitted via contact with blood and other body fluids. We therefore assessed the knowledge, attitude and practice (KAP) of infection prevention and control (IPC) one year after an outbreak of nosocomial transmission of Lassa fever in the study hospital. Methodology: A cross-sectional study of HCWs was conducted in Alex Ekwueme Federal University Teaching Hospital, Abakaliki, Ebonyi State, a tertiary hospital designated for Lassa fever treatment in southeast Nigeria. A total of 631 HCWs selected by systematic random sampling were surveyed using self-administered questionnaire to determine the KAP of IPC. Data analysis was done with EPI INFO version 7.2 and Microsoft Excel 2016, and Chi square statistic was used to examine relationship between variables at 5% level of significance. Results: Only 287 (51.1%) of the 562 respondent HCWs had good knowledge of IPC, 442 (78.6%) had good attitude towards IPC, and 268 (47.7%) had good practice of IPC. Socio-demographic predictors of IPC knowledge included being a medical laboratory scientist (AOR=0.5; 95% CI=0.29-0.83; p=0.009), tertiary education level (AOR=7.0; 95% CI=1.11-44.60; p=0.038), and work experience of ≥ 7 years (AOR=2.3; 95% CI=1.47-3.57; p<0.001). Male gender (AOR=1.9; 95% CI=1.06-3.42; p=0.031), nurse professional (AOR=6.5; 95% CI=2.67-15.81; p<0.001) and work experience of ≥ 7 years (AOR=2.5; 95% CI=1.37-4.54; p=0.003) were predictors of good attitude towards IPC. Also, nurse professional (AOR=3.1; 95% CI=1.79-5.20; p<0.001) and married status (AOR=1.6; 95% CI=1.05-2.55; p=0.028) were predictors of good practice of IPC among the respondents. Conclusions: The study demonstrated that knowledge and practice of IPC was low in the study location despite the interventions that had been instituted to improve the IPC framework. Therefore, there is need to adapt approaches that will influence behavior change towards IPC in the course of the in-service trainings being conducted in the hospital.

Lassa fever coinfection with COVID-19 among health care workers: Report of two cases

Lassa fever (LF) coinfection with hepatitis B and HIV has been reported among hospitalized patients in Southwest Nigeria and HIV patients coinfected with COVID-19 have been described among hospitalized patients in North Central Nigeria, no study has reported cases of coinfection of Lassa disease and COVID-19 among health care workers (HCWs) worldwide. A case report of two HCWs who were infected with both LF virus and SARS-CoV-2 virus at same time and were successfully managed without any sequelae. Both cases presented with typical signs of LF with COVID-19 suspected, they were promptly diagnosed with positive outcomes after treatment. While case 1 became negative for LF virus and SARS-CoV-2 after 6 and 30 days, respectively, case 2 became negative for both viruses after 14 and 32 days, respectively. The diagnosis of LF-COVID-19 coinfection in HCWs is a frightening dimension to the health risks faced by HCWs, therefore, HCWs now more than ever before want to know what comes next and how safe is the practice of medicine.

Preparedness of Nigerian Health Institutions toward managing Lassa Fever Epidemic and Covid­19 Pandemic

Objectives: The objective is to assess standard practice of healthcare workers and preparedness of their healthcare institutions toward controlling spread of infectious diseases. Background: With the on ­ going epidemic of Lassa fever and the rising incidence of Covid­19 pandemic in Nigeria, there has been efforts from government and stakeholders in health towards controlling the surge of these diseases. This study is a multi­center survey involving frontline health­care workers, from 102 health institutions.Methodology: Pretested self­administered questionnaires were sent through online Google form to health­care workers across various health institutions through their respective social media platforms. Their consent was sought and the questionnaires were filled through registered emails. Multiple entry from same individual was prevented. The number of respondents was 451. The information gathered include biodata of health­care workers, details of their cadre and years of practice, their level of standard precautions and preparedness of their health institutions. Data gathered were collated, summarized, and analyzed using simple tables with proportions.Results: The practice of standard precaution was inadequate with only 59.4% of respondents washing their hands regularly after touching patients or carrying out procedures, while only 34.4% of them used face masks while consulting patients with respiratory symptoms. As for preparedness of health institutions in control of Lassa fever and Covid­19, 63.1% and 77.6% of respondents affirmed that their health institutions had written protocol of managing infectious diseases and had organized workshop on Lassa fever and/or Covid­19, respectively, while only 45.5% and 20% of respondents had dedicated isolation wards and functional intensive care units in their health institutions.Conclusion: The standard safety precautions by health­care workers were suboptimal and preparedness of their health institutions was generally inadequate for the management and control of infectious diseases

A Knowledge, attitude and practice (KAP) analysis of lassa fever media campaigns among residents of South-East Nigeria

Background: In as much as studies have been conducted on Lassa fever in Nigeria, the studies had no media angle and were carried out mainly in the Northern and Western regions of the country. This study examined how mass media intervention messages on Lassa fever have influenced the level of knowledge, attitudes and health practices of people living in South-East Nigeria towards controlling and eradicating this disease. Methods: The study adopted survey research design. Multi-stage sampling technique was used in selecting 428 respondents while structured questionnaire was used for data collection.Data analyzed was by descriptive statistics and Pearson correlation technique. Result: The level of exposure to and knowledge of Lassa fever media campaigns among South-East residents were high as confirmed by 90% and 51.1% respectively of the responses. Media campaigns against Lassa fever positively influenced the attitudes of 56.3% of the respondents towards prevention and control of this disease.There is positivesignificant relationship (0.93 with 0.01 level of significant) between exposure level to Lassa fever media campaigns and knowledge level of the disease among South-East residents. Conclusion: Mass media campaigns aimed at sensitizing the public on Lassa fever disease was adjudged effective. There is also need to employ more of interpersonal communication strategies to enhance effective delivery of this health messages

Lassa fever awareness and knowledge among community residents in Ondo State, Nigeria

Background: The Lassa fever outbreak in Ondo State in 2018 recorded high morbidity and mortality. This study was conducted to assess awareness and knowledge of Lassa fever preventive measures among community residents in the affected areas in order to guide risk communication interventions. Methods: A community-based descriptive cross-sectional study was conducted in six affected Local Government Area (LGAs), involving heads of households selected using a multistage sampling technique. A structured pre-tested questionnaire was administered to 2992 consenting study participants and data was analysed using IBM Statistical Package for Social Sciences version 20.0. Results: Over three quarters 2, 537 (84.8%) of respondents were aware of Lassa fever of which 2, 363 (93.1%) knew that multimammate rat transmits the disease to humans. Also, 1804 (71.1%) knew that washing hands regularly could prevent the disease. However, only 845 (33.3%) of the respondents who reported awareness of the disease knew that cooking all foods properly before eating could prevent the disease. The predictors of good knowledge of Lassa fever were being a female (p= 0.017), having secondary or tertiary education (p=0.001), and currently married or divorced (p=0.01). Conclusion: A high level of awareness, but inadequate knowledge of some preventive measures of Lassa fever were observed among community members. Risk communication messages should focus more on preventive measures of the disease targeting young males with low education in these LGAs, the epicentres of the outbreak

Lassa fever awareness and knowledge among community residents in Ondo State, Nigeria

Background: The Lassa fever outbreak in Ondo State in 2018 recorded high morbidity and mortality. This study was conducted to assess awareness and knowledge of Lassa fever preventive measures among community residents in the affected areas in order to guide risk communication interventions. Methods: A community-based descriptive cross-sectional study was conducted in six affected Local Government Area (LGAs), involving heads of households selected using a multistage sampling technique. A structured pre-tested questionnaire was administered to 2992 consenting study participants and data was analysed using IBM Statistical Package for Social Sciences version 20.0. Results: Over three quarters 2, 537 (84.8%) of respondents were aware of Lassa fever of which 2, 363 (93.1%) knew that multimammate rat transmits the disease to humans. Also, 1804 (71.1%) knew that washing hands regularly could prevent the disease. However, only 845 (33.3%) of the respondents who reported awareness of the disease knew that cooking all foods properly before eating could prevent the disease. The predictors of good knowledge of Lassa fever were being a female (p= 0.017), having secondary or tertiary education (p=0.001), and currently married or divorced (p=0.01). Conclusion: A high level of awareness, but inadequate knowledge of some preventive measures of Lassa fever were observed among community members. Risk communication messages should focus more on preventive measures of the disease targeting young males with low education in these LGAs, the epicentres of the outbreak

Mass media awareness campaign and the prevention of the spread of Lassa fever in the rural communities of Ebonyi State, Nigeria: Impact evaluation

This paper investigates the impact of media campaign on the prevention and spread of Lassa fever in Ebonyi state. 354 respondents were randomly selected from six rural communities in the state as study sample, while structured questionnaires were used for collecting data. SPSS version 20.0 was used to analyze the data. Results of analysis reveal that the media campaign has rural reach but has little or no impact. The results also reveal that the campaign failed to create appropriate awareness of the disease, its preventive/curative health behaviors. It further reveals that there are no health behavior modifications among the people because of the campaign. Therefore, this paper recommends the modification of media contents to incorporate the required preventive/curative health behaviors. Secondly, mandatory mass media awareness campaign and jingles in every news hour is recommend

Connaissances et attitudes des relais communautaires sur les fièvres hémorragiques à virus Lassa et Ebola dans le département de la Donga (Nord Bénin)

Introduction: l'objectif de cette étude était d'évaluer les connaissances et attitudes des relais communautaires vis-à-vis des fièvres hémorragiques à virus Ebola et Lassa et leur implication dans la mise œuvre des activités de prévention de ces maladies.Méthodes: une enquête transversale descriptive a été menée auprès des relais communautaires recrutés par tirage au sort dans 40 villages du département de la Donga. Ces relais faisaient la prise en charge à domicile des maladies respiratoires, diarrhéiques et du paludisme chez les enfants de moins de cinq ans. Un questionnaire anonyme a été administré par interview directe. Les données ont été analysées à l'aide du logiciel Epi-info 3.5.1.Résultats: au total 58 relais communautaires (RC) ont participé à cette enquête sur les 60 attendus. L'âge moyen était de 38,7±10,6 ans avec un sex-ratio de 3,5. Il y avait majoritairement trente cinq cultivateurs (60,3%) et treize revendeuses (22,4%). Quarante huit enquêtés (82,8%) reconnaissaient les deux maladies comme étant graves, mortelles et transmissibles. Les trois principales voies de transmission citées étaient le contact ou la consommation de gibiers (87,9%), le contact direct avec les personnes infectées (74,1%) ou leurs cadavres (46,6%). Les principaux moyens préventifs énumérés étaient en lien avec les voies de transmission. La fièvre (81,0%), les vomissements (81,0%) et la diarrhée (60,3%) venaient en tête des symptômes cités. Seulement vingt-deux RC (37,9%) disposaient de gants mais les utilisaient rarement pour examiner les enfants malades. Quant à la conduite à tenir devant un cas suspect de fièvre hémorragique virale Lassa ou Ebola, quarante-et-un relais communautaires (70,7%) feraient recours aux agents de santé sans toucher au malade, neuf (15,5%) feraient appel à l'ambulance et huit (13,8%) transporteraient le cas sur leur propre moto ou sur un taxi-moto vers le centre de santé le plus proche. Conclusion: le renforcement des capacités des relais communautaires sur les fièvres hémorragiques virales contribuerait à l'amélioration de leurs connaissances sur ces épidémies mortelles et à la qualité de leurs interventions dans la population

Molecular confirmation of lassa fever imported into Ghana

Background: Recent reports have shown an expansion of Lassa virus from the area where it was first isolated in Nigeria to other areas of West Africa. Two Ghanaian soldiers on a United Nations peacekeeping mission in Liberia were taken ill with viral haemorrhagic fever syndrome following the death of a sick colleague and were referred to a military hospital in Accra; Ghana; in May 2013. Blood samples from the soldiers and five asymptomatic close contacts were subjected to laboratory investigations.Objective: We report the results of these investigations to highlight the importance of molecular diagnostic applications and the need for heightened awareness about Lassa fever in West Africa.Methods: We used molecular assays on sera from the two patients to identify the causativeorganism. Upon detection of positive signals for Lassa virus ribonucleic material by two different polymerase chain reaction assays; sequencing and phylogenetic analyses were performed.Results: The presence of Lassa virus in the soldiers' blood samples was shown by L-gene segment homology to be the Macenta and las803792 strains previously isolated in Liberia; with close relationships then confirmed by phylogenetic tree construction. The five asymptomatic close contacts were negative for Lassa virus.Conclusions: The Lassa virus strains identified in the two Ghanaian soldiers had molecular epidemiological links to strains from Liberia. Lassa virus was probably responsible for the outbreak of viral haemorrhagic fever in the military camp. These data confirm Lassa fever endemicity in West Africa

The Sensitivity and Specificity of Lassa Virus IgM by ELISA as Screening Tool at Early Phase of Lassa Fever Infection

"Background: Early diagnosis; prompt treatment; and disease containment are vital measures in the management of Lassa fever (LF); a lethal and contagious arenaviral hemorrhagic disease prevalent in West Africa. Lassa Virus (LAV)-specific Reverse Transcriptase Polymerase Chain Reaction (RT-PCR) test; the gold standard for diagnosis; is unavailable in most centers. Serologic detection of LAV IgM is a more accessible tool and this work was to investigate its adequacy as an early marker for LF. Patients and Methods: A prospective case-control study conducted July 2007-March 2011 in a tertiary referral health center in Nigeria. Blood samples for test and control were evaluated for Lassa specific antigens and IgM using RT-PCR (primers S36+ and LVS 339) and indirect ELISA (Lassa Nucleo-protein (NP)-Antigen) respectively. RT-PCR outcome was used as standard to test for the sensitivity and specificity of IgM. Results: Of the 37 confirmed cases of LF infection by RT-PCR; 21 (57) were IgM positive. Amongst the 35 confirmed negative cases (control group); eight were IgM positive. The diagnostic sensitivity and specificity of the IgM assay were 57 and 77 respectively. The negative and positive predictive values of the IgM serological assay were 63 and 72 ; respectively; while the efficiency of the test was 67. Conclusion: The specificity and sensitivity of IgM as a screening tool for early detection of LF appear weak and; hence; the need for a reliable LF ""rapid screening kit"" since RT-PCR is unavailable in most centers. In the interim; ""high clinical index of suspicion;"" irrespective of IgM status; requires urgent referral to confirmatory centers."

Lassa Fever: another infectious menace

Nigeria is presently suffering from another Lassa fever epidemic. This was confirmed in the statement of the Minister of Health of the Federation in which he said; ""There has been an upsurge in the reported cases of Lassa fever since the beginning of this year; especially in the Federal Capital Territory and its environs. Within two weeks; 12 cases with five deaths due to the disease were recorded. 25 contacts are confirmed by laboratory investigations to have been infected; including 4 health staff working in the National Hospital; Abuja.""1 Lassa fever is an acute viral haemorrhagic fever first described in 1969 in the town of Lassa in Borno state; Nigeria.2 It is endemic in West African countries; and causes 300;000 cases annually with 5000 deaths.3 Lassa fever epidemics occur in Nigeria; Liberia; Sierra Leone; Guinea and the Central African Republic.4 Lassa virus; the agent of the disease is a member of the Arenaviridae family. The virus is pleomorphic with single-stranded and bisegmented RNA genome.3 Its primary host is Natal Multimammate Mouse (Mastomys natalensis). Transmission to man occurs via exposure to the rat excrement through respiratory or gastrointestinal tracts5; exposure of broken skin or mucus membrane to infected material; direct contact; sexually and transplacentally. The prevalence of antibodies to the virus is 8-229 in Sierra Leone; 4-55in Guinea;12 and 21in Nigeria.13 The disease is mild or asymptomatic in 80of infected people; but 20have a severe multisystemic disease. Clinical features are difficult to differentiate from that of other viral haemorrhagic fevers and common febrile illness such as Malaria; Typhoid fever and so on. Definitive diagnosis is by viral isolation; Antigen and Antibody detection and Reverse Transcriptase PCR. Treatment is with Ribavirin; an antiviral agent. No vaccine is currently available. Prevention is by keeping rats away from homes

Lassa fever in West African sub-region: an overview.

Lassa fever is an acute viral zoonotic illness caused by Lassa virus, an arenavirus known to be responsible for a severe haemorrhagic fever characterised by fever, muscle aches, sore throat, nausea, vomiting and, chest and abdominal pain. The virus exhibits persistent, asymptomatic infection with profuse urinary virus excretion in the ubiquitous rodent vector, Mastomys natalensis. Lassa fever is endemic in West Africa and has been reported from Sierra Leone, Guinea, Liberia, and Nigeria. Some studies indicate that 300,000 to 500,000 cases of Lassa fever and 5000 deaths occur yearly across West Africa. Studies reported in English, that investigated Lassa fever with reference to West Africa were identified using the Medline Entrez-PubMed search and were used for this review. The scarcity of resources available for health care delivery system and the political instability that characterise the West African countries would continue to impede efforts for the control of Lassa fever in the sub-region. There is need for adequate training of health care workers regarding diagnostics, intensive care of patients under isolation, contact tracing, adequate precautionary measures in handling infectious laboratory specimens, control of the vector as well as care and disposal of infectious waste.

Emerging and reemerging zoonotic diseases

Zoonoses are disease and/or infection naturally transmissible between vertebrate animals and humans, Emerging zoonoses are defined by the WHO/FAO/OIE joint consultation on emerging zoonotic disease held in Geneva, 3-5 may 2004 as "diseases which are newly recognized are newly evolved or that have occurred previously but show an increase in incidence or expansion in geographical, host or vector range". The number of emerging zoonoses has increased dramatically over the lost few decades, with potentially serious human and economic impact worldwide. Many factors are behind the emergence of these zoonotic diseases. Intensive animal husbandry and changes in the production and distribution of food and other commodities, climatic and environmental charges, rapid transportation of human and animals, changes in life style and increased animal contacts are some of the factors that could introduce a new disease in a particular area. Viral infectious agents are more prone to mutation and sudden or gradual change and expansion to new geographical areas or hosts. In this article we briefly discuss some of the zoonotic diseases which may have potential health effects in Iran, such as avian influenza, West Nile viruses, Rift Valley fever, Congo-Crimean hemorrhagic fever, Lassa fever, Sars, and Ebola Morburg hemorrhagic disease

Detection des anticorps anti-virus de Lassa dans l'ouest forestier de la Cote d'Ivoire

La fievre de Lassa est une fievre hemorragique virale (FHV) africaine endemique en Afrique de l'Ouest; notamment au Nigeria; en Sierra Leone; au Liberia et en Guinee. La Cote d'ivoire qui part age des frontieres avec le Liberia et la Guinee n'a jamais notifie de cas de fievre de Lassa. Dans le cadre d'un projet de recherche sur les fievres hemorragiques virales principalement la fievre jaune; la fievre de Lassa et la fievre Ebola en Guinee et en Cote d'Ivoire; une enquete a ete realisee en mars 2000 chez des travailleurs forestiers des prefectures de Guiglo et Duekoue; dans le but de determiner le niveau de connaissance sur les fievres hemorra-giques virales et le statut immunitaire vis a vis du virus de Lassa. Cent soixante-trois sujets de sexe masculin professionnels de la foret ont ete interroges a l'aide d'un questionnaire sur les facteurs de risque d'exposition aux FHV et leurs antecedents medicaux des 12 dern i e rs mois. Les anticorps seriques de type IgG anti-virus de Lassa ont ete detectes par technique d'immunofluorescence utilisant les antigenes Lassa des souches Josuah et LAS/AV. La prevalence globale en IgG obtenue etait de 26(42/161). Pa rmi les sujets positifs; 38;5etaient des bucherons dont 20positifs au 1/40; 46;7des agents du parc national ou gardes forestieres dont 69positifs au 1/40 et plus. De plus; 41des sujets avaient entendu parler des FHV; 14ont attribue leur origine a des animaux et 2a des plantes. Les contacts avec les rongeurs etaient frequents et plus de 50des personnes ont deja consomme ou depece des rongeurs. La proportion de sujets porteurs d'anticorps IgG anti-virus de Lassa dans cette population semblait elevee. Cependant cette prevalence ne permet pas de conclure a une exposition particuliere au virus de Lassa