**2. Aspect of Lassa virus structure**

Lassa fever virus (LASV) is a member of the family Arenaviridae ("*Arena*" means "*Sand*" in Latin root) [16, 17]. The virus is single-stranded, bisegmented, ambisense RNA virus. Arenaviruses are classified as segmented negative-sense RNA (nsRNA) viruses and are phylogenetically closely related to other segmented nsRNA viruses belonging to the family *Bunyaviridae* and *Orthomyxoviridae* [9, 18]. The three virus families share similar characteristics of the intracellular replication cycle. It is round, oval, or pleomorphic, 110–130 nm in diameter, and has a protective envelop. LASV differ from 10 to 19 kilobases and contains two RNA species, which are the big and small units [11, 19]. The two genes at different point do not cross exist in every unit [20, 21]. The genetic material that encodes nucleoprotein is 1710 nucleotides in length and the protein has 569 amino acids and that of glycoprotein is 1473 nucleotides long. The viral agent has four lineages, which differ in strain by 27% in respect to their nucleotides and 15% in respect to amino acids [22]. In the virus, the 3′ half of the genetic material has a negative polarity and the 5′ half is of a positive polarity that makes few virus proteins to encode in virus-complementary subgenomic mRNA species, while other viral proteins are encoded in virus-sense subgenomic mRNA sequences. The replication strategy (Ambisense) of the virus is somewhat seldom among viruses and thus distributed among groups of the Arenaviridae [15, 18].

of new viruses. However, these RNAs do not seem to have a required function in virus replication cycle and new work by the Viral Hemorrhagic Fever Consortium [23] sheds suspicion on

A Reemerging Lassa Virus: Aspects of Its Structure, Replication, Pathogenicity and Diagnosis

http://dx.doi.org/10.5772/intechopen.79072

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Lassa virus adopts a replication strategy known as "*Ambisense*," which is very rapid and demonstrates the replication of temporal control [24]. The initial stage of transcription of mRNA

whether these sandy granules are indeed host ribosomes (**Figure 1**).

**Figure 1.** The Virion and genome having the L and S segments [15, 17, 21, 23].

**3. How Lassa virus replicates**

The virus envelope is gotten when new particles bud off through the plasma membrane of the host cell and it carries club-shaped surface projections that are about 10 nm long [4, 19]. Sandy-appearing granules that resemble ribosomes are found within the unstructured interior

It is a reemerging virus with a select agent, which requires Biosafety Level 4-equivalent containment [7]. It is endemic in West African countries including Sierra Leone, the Republic of Guinea, Nigeria, and Liberia, where cases of the infection is between 300,000 and 500,000 yearly resulting in 5000 deaths annually [4, 8, 9]. About 80% infected with the virus are asymptomatic and 1 in 5 infection results in severe disease, where the virus affects several organs such as the liver, spleen, and kidneys [10]. The virus is harbored by the multimammate rats of the genus *Mastomys* and transmitted to Mans through primary aerosols of the rat's urine, close contact with urine, feces, saliva, or ingestion of contaminated foods of the rat [11]. LASV is also spread through contaminated hospital equipment but interestingly, it cannot be contracted by humans to humans only via bodily fluids contacts [12]. Findings have reported the presence of the virus in seminal fluids up to 3 months after infection of the virus. Research to show that Lassa virus can be gotten via sexual intercourse has not been reported but there are speculations that LASV might possibly be used for bioterrorism, so it is now being studied

Due to the variability of the clinical course of the disease, detection of the disease in affected patients has been challenging. When presence of the virus is confirmed in a locality, quick isolation of infected patients, good infection prevention and control practices, and rigorous

Lassa fever virus (LASV) is a member of the family Arenaviridae ("*Arena*" means "*Sand*" in Latin root) [16, 17]. The virus is single-stranded, bisegmented, ambisense RNA virus. Arenaviruses are classified as segmented negative-sense RNA (nsRNA) viruses and are phylogenetically closely related to other segmented nsRNA viruses belonging to the family *Bunyaviridae* and *Orthomyxoviridae* [9, 18]. The three virus families share similar characteristics of the intracellular replication cycle. It is round, oval, or pleomorphic, 110–130 nm in diameter, and has a protective envelop. LASV differ from 10 to 19 kilobases and contains two RNA species, which are the big and small units [11, 19]. The two genes at different point do not cross exist in every unit [20, 21]. The genetic material that encodes nucleoprotein is 1710 nucleotides in length and the protein has 569 amino acids and that of glycoprotein is 1473 nucleotides long. The viral agent has four lineages, which differ in strain by 27% in respect to their nucleotides and 15% in respect to amino acids [22]. In the virus, the 3′ half of the genetic material has a negative polarity and the 5′ half is of a positive polarity that makes few virus proteins to encode in virus-complementary subgenomic mRNA species, while other viral proteins are encoded in virus-sense subgenomic mRNA sequences. The replication strategy (Ambisense) of the virus is somewhat seldom among viruses and thus distributed among groups of the

The virus envelope is gotten when new particles bud off through the plasma membrane of the host cell and it carries club-shaped surface projections that are about 10 nm long [4, 19]. Sandy-appearing granules that resemble ribosomes are found within the unstructured interior

at greater lengths [13, 14].

Arenaviridae [15, 18].

contact tracing can help halt epidemicity [15].

152 Current Topics in Tropical Emerging Diseases and Travel Medicine

**2. Aspect of Lassa virus structure**

**Figure 1.** The Virion and genome having the L and S segments [15, 17, 21, 23].

of new viruses. However, these RNAs do not seem to have a required function in virus replication cycle and new work by the Viral Hemorrhagic Fever Consortium [23] sheds suspicion on whether these sandy granules are indeed host ribosomes (**Figure 1**).
