**1. Introduction**

Lassa virus (LASV) is first described in the 1950s [1] but not identified until 1969 in Jos, Nigeria [2, 3]. The virus causes Lassa fever that is hemorrhagic in nature, which is severe and fatal. It affects 2–3 million people annually [4, 5] and has been known to be endemic in Benin Republic in 2014, Ghana in 2011, Guinea, Liberia, and Mali in 2009, Sierra Leone, and Nigeria [3, 4, 6], but probably exists in other West African countries as well [4].

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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 at greater lengths [13, 14].

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 contact tracing can help halt epidemicity [15].
