BACKGROUND OF THE STUDY
Lassa fever (LF) is a viral hemorrhagic zoonotic disease caused by an arenavirus. Humans get infected with the virus primarily through ingestion of food or food substances contaminated with the excreta of Mastomysnatalensis rodent (Olugasa, Dogba, Ogunro, Odigie, Nykoi, Ojo, et al (2012) commonly known as the Multimammate rat), which is the natural reservoir for the virus. Human to human transmission is also possible through contact with secretions and excretions of infected persons. Lassa fever is predominant in West Africa including Sierra Leone, Liberia and Nigeria (Bond, Schieffelin, Moses, Bennett & Bausch, 2013). It affects 100,000 to 300,000 people every year in this region (Asogun, Adomeh, Ehimuan, Odia, Hass & Gabriel, et al 2012).There have been several LF outbreaks in various parts of Nigeria and the largest outbreak ever reported was in 2018 which shows an increasing trend in the number of cases and deaths (Ilori, Frank, Dan-Nwafor, Ipadeola, Krings & Ukponu, et al, 2018). In 2018, a total of 3016 suspected Lassa fever cases were reported from 22 states. Of these cases, 559 were confirmed positive, 17 probable and 2440 negative. The case fatality rate among confirmed cases was 25.6 % and 100 % among probable cases. All the affected 22 states had at least one confirmed case spreading through 90 Local Government Areas (LGAs). Three of the 22 affected states constituted 83.0% of the confirmed cases: Edo (46%), Ondo (24%) and Ebonyi (13%) states (Ilori, Frank, Dan-Nwafor, Ipadeola, Krings & Ukponu, et al.(2018.). Edo State is one of the states in Nigeria with high burden of LF cases with occurrence all through the year. The first outbreak of LF in Edo State occurred in Esan West LGA in 2016 (Asogun, Adomeh, Ehimuan, Odia, Hass & Gabriel, et al, 2012; Tobin, Asogun, Akpede, Adomeh, Odia & Gunther, 2015). Identification of primary spatial clusters have contributed immensely to understanding disease risk behavior as well as help guide and inform prioritization of public health intervention strategies (Moise, Kalipeni, 2012). Studies have indicated that habitat suitability such as agricultural intensification associated with post-harvest grain, storage density on residential areas could significantly influence Mastomys breeding and transmission of the Lassa virus to humans (Olugasa, Dogba, 2012; Olugasa, Dogba, Ogunro, Odigie, Nykoi & Ojo, et al, 2012). Geographic information system (GIS) and spatial models have been used to gain better understanding about the risk distribution of LF along West Africa sub-region (Anselin, Syabri, Kho & GeoDa (2016).
The disease is responsible for recurrent epidemics of acute haemorrhagic fever in parts of West Africa as well as sporadic disease in Europe, Asia and America [Monath, 2010; Macher & Wolfe, 2016] . The Lassa virus is a likely agent of bioterrorism, with capacity for person to person transmission and potential to cause hospital outbreaks with attendant morbidity and mortality among health workers[Khan & Goba, 2018] . The earliest cases of Lassa fever were thought to have occurred between 1920 and 1950, in Nigeria, Sierra Leone and Central African Republic and perhaps in other West African countries [Monath, 2010] . However, the disease became recognized and named in 1960 after two missionary nurses died and a third suffered a grave apparently communicable febrile systemic illness while working in Nigeria [Frame, John, Baldwin & Gocke, 2015] . The index patient was working in a mission hospital in Lassa town, Borno State, North-Eastern Nigeria when she fell critically ill and was transferred to Evangel Hospital, Jos Plateau State (now Bingham University Teaching Hospital, Jos) where she subsequently died. The second nurse, who was a staff of Evangel Hospital, cared for the index patient on presentation and she later developed comparable symptoms like the index case culminating in her death days later. The third nurse was also a staff of Evangel Hospital who cared for both patients. She also fell progressively ill and had to be transferred to the United States of America for further management and definitive diagnosis. Fortunately she survived and recovered almost completely except for scalp hair loss. Serum samples and body fluids retrieved from all these patients were later shown to be positive of a novel virus which was named “LASSA virus‟ and the disease named “Lassa fever” in recognition of Lassa town where the index case of the disease was first documented [Frame, John, Baldwin & Gocke, 2015] .
The Lassa virus is a single stranded RNA virus belonging to the Arenaviridae family of viruses [Peters, 2010] . The virus is often named haemorrhagic fever virus because of the tendency to cause bleeding from body orifices. It is round, oval, or pleomorphic, 110 to 130 nm in diameter, and enveloped [Peters, 2010; Ogbu & Ajuluchukwu 2013] . Its genome consists of two single-stranded RNA segment – the large L segment and the small S segment. The large segment encodes the viral polymerase and zinc binding protein and the small segment encodes the structural proteins – nucleoprotein and glycoprotein precursor. The virus is inactivated by heating from 56–100˚C, ultraviolet and gamma radiations and pH range between 5.5 and 8.5, as well as by chemical agents like 0.5% sodium hypocrite, 0.5% phenol, 10% formalin and detergents. [Peters, 2010; Ogbu & Ajuluchukwu, 2013; Ehichioya , Hass & Becker-Ziaja, 2011] Sequencing of the small segment of the RNA of Lassa virus has revealed the presence of four major lineages in West Africa: three in Nigeria (lineages I, II, and III) and one in the area comprising Ivory Coast, Sierra Leone, Liberia, and Guinea (lineage IV)[Ehichioya, Hass & Becker-Ziaja B 2011] . Various viral strains have been associated with these major lineages with differences their genetic, serologic, and pathogenic characteristics [Ehichioya, Hass & Becker-Ziaja, 2011] .Lassa fever has accounted for recurrent outbreaks of acute haemorrhagic fever in Nigeria since the discovery of the virus in Lassa town northeastern Nigeria in 1969. The prevalence of antibodies to the virus in Nigeria is 21% [Tomori, Fabiyi, Sorungbe, Smith & McCormick, 2015] as compared to 8-22% in Sierra Leone [McCormick, Webb, Krebs, Johnson & Smith, 2017] and 4-55% in Guinea[Bausch, Demby, Coulibaly, Kanu, Goba & Bah, et al 2011] . In the last 50 years more than 28 states in Nigeria and the Federal Capital Territory have experienced one or more outbreaks of Lassa fever. Nigeria that have been reported in the literature and by the Federal ministry of health, Nigeria from 1969 to 2016.[Monath, 2010; Frame, John, Baldwin, Gocke & Troup2015; Troup, White, Fom & Carey, 2015; Fisher-Hoch, Tomori, Nasidi, Perez-Oronoz, Fakile & Hutwagner, et al 1995; Grundy, Bowen & Lloyd, 1980; Bowen, Tomori, Wulff, Casals, Noonan, Down 2010; Biya & Coker, 2013] Outbreaks were also reported in various states in Nigeria between 2018 and 2011 [Ehichioya, 2012; Inegbenebor, 2010; Ehichioya, 2010; WHO, 2011] . The last outbreak of Lassa fever in Nigeria began in December 2011 and as at 17th August 2012, a total of 934 suspected Lassa fever cases, 147 Laboratory confirmed and 93 deaths (CFR 9.97%) were reported from 41 LGAs in 23 States In states that have yet reported a case or an outbreak of Lassa fever since 1969, it is possible that cases of Lassa fever were either unrecognized or not reported. Edo state has so far recorded the highest incidence of outbreaks of Lassa fever in Nigeria. This may be partly due to improve surveillance compared to other states, as one of the major diagnostic centers for Lassa fever in Nigeria is situated in Edo state. In a study conducted at Iruua Specialist Teaching Hospital, in Edo state, Lassa fever accounted for 7% of the admissions and 13% of deaths in the adult medical wards of Irrua Specialist Teaching Hospital in 2013 [Inegbenebor & Okosun, 2010] These rates are lower than the findings in a similar study in Sierra Leone in 2017, in which Lassa fever was found to be responsible for 10–16% of admissions and 30% of adult deaths in the medicine department of a major referral centre [McCormick, 2017] . Edo State is one of the states in the South – south geo-political zone of Nigeria which has had one of the highest outbreak of Lassa fever in the recent years ; lying on 05’44 N and 07’34 N latitudes, 05’ 4 E and 06’45 E longitudes, and mostly tropical rain forest. Administratively, it has 3 senatorial zones (Edo North, Edo Central and Edo South), 18 LGAs and 192 wards. The 2018 projected human population for Edo State from the 2016 national population census was 4,600,000. Agriculture is the main occupation of the people (FGN 2019). Edo State has 472 health facilities with 55 private health facilities and the Institute for Lassa fever Research. Esan West LGA has the highest burden of Lassa fever cases from the LGAs and contributes more than 70% of cases reported in this LGA. The reason(s) for this burden are unclear. We conducted this study to determine the risk factors associated with high burden of Lassa fever and assess the way forward in Esan West community.
STATEMENT OF THE PROBLEM
Lassa fever is one of the common diseases in Edo state especially in Esan west local government of Edo state. AS a result of a rising case of this disease it has affected or has an impact on the communities in this local government. This has been a problem to the indigenes of this state because this disease doesn’t only affect their health; it affects other parts of their lives as a result of Lassa fever which has been an issue. Despite Edo state hosting the institute for Lassa fever research and control this state has recorded one of the highest cases of Lassa fever in recent times in Nigeria. This study examines a critical study on the rising case of Lassa fever in Esan West Local Government of Edo State.
OBJECTIVE OF THE STUDY
The main purpose of this study is to examine a critical study on the rising case of Lassa fever in Esan west local government area In Edo state. The specific objectives are:
1) To examine the level of Lassa fever in Esan west local government area in Edo state
2) To investigate the causes of Lassa fever in Esan west local government area.
3) To examine the impact of Lassa fever in Esan west local government area.
4) To examine the measures of controlling Lassa fever in Esan west local government area.
5) To recommend ways of preventing Lassa fever in Esan west local government area.
1) What is the level of Lassa fever in Esan West local government area in Edo state?
2) What are the causes of Lassa fever in Esan West local government area?
3) What is the impact of Lassa fever in Esan West local government area?
4) What are the measures of controlling Lassa fever in Esan West local government area?
5) What are the ways of preventing Lassa fever in Nigeria Esan West local government area?
H0: The rising case of Lassa fever has no significant impact on the morbidity and mortality rate of Esan west local government area.
H1: The rising case of Lassa fever has a significant impact on the morbidity and mortality rate of Esan west local government Area.
SIGNIFICANCE OF THE STUDY
The study would have contribution to enlighten the society on the critical rising case of Lassa fever in Esan West local government area in Edo state. The study will enable relevant agencies concerned with eradicating Lassa fever in Esan West L.G.A, Edo state and Nigeria in general to appraise the media framework for possible modification or modernization. It would also prepare ground for interested researcher who might wish to conduct further research in related areas and could contribute to the existing literature.
SCOPE OF THE STUDY
The study is restricted to the critical study on rising of Lassa fever in Esan west local government area of Edo state.
LIMITATION OF THE STUDY
Financial constraint: Insufficient fund tends to impede the efficiency of the researcher in sourcing for the relevant materials, literature or information and in the process of data collection (internet, questionnaire and interview)
Time constraint: The researcher will simultaneously engage in this study with other academic work. This consequently will cut down on the time devoted for the research work.
DEFINITION OF TERMS
Lassa fever: Lassa fever is an acute viral haemorrhagic illness caused by Lassa virus, a member of the arena virus family of viruses. Humans usually become infected with Lassa virus through exposure to food or household items contaminated with urine or faeces of infected Mastomys rats.
Morbidity Rate: Refers to having a disease or a symptom of disease, or to the amount of disease within a population. Morbidity also refers to medical problems caused by a treatment.
Mortality: Mortality rate, or death rate, is a measure of the number of deaths (in general, or due to a specific cause) in a particular population, scaled to the size of that population, per unit of time.