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Lassa virus (LASV) is classified into genus Mammarenavirus of Arenaviridae family. This virus is etiological agent of Lassa fever (LF) which is widespread in Africa. On average, in four out of five infected people, LF occurs without symptoms. The annual incidence ranges from 100,000 to 500,000 registered clinical cases, at a mortality rate of 1-2%. Among hospitalized patients with severe symptoms of hemorrhagic fever, this figure may be from 14 to 89.5%. Signs of an adverse outcome in LF are open bleeding and disorders of CNS (convulsions, tremor, disorientation and coma). Death occurs from multiple organ failure. Severely ill people recover slowly and may have relapses and complications such as pneumonia, myocarditis, psychosis, and hearing loss.Transmission of the virus in endemic territories occurs by alimentary way, air-dust and airborne droplets from a zoonotic source – rodents of the species African multimammate rat (Mastomys natalensis), by accidental contacts of people with their secretions (urine, feces, saliva) as well as when butchering carcasses and eating rodents. These animals are characterized by asymptomatic carrier and life-long persistence of the virus. Cases of transmission of the virus from person to person through the blood or other body fluids of patients are described. A sick person is contagious for two months, because the virus circulates in the blood despite high levels of antibodies. Infection of medical staff occurs during emergency surgical operations, or when the rules of contact precautions are not observed. Currently, with the ongoing LF outbreak in Nigeria, since 2016, hospitals have registered mortality rates of 22 and 8% for patients and health workers, respectively. During 1969-2016, 33 imported cases of this disease were described from West Africa to non-endemic territories (in the USA, Canada, Great Britain, the Netherlands, Germany, Israel and Japan). The mortality rate among these patients was 39%.The lack of prophylactic vaccines and specific therapeutic drugs is the major challenge for the prevention of LF. Thus, this review considers biological models (cell cultures and animals) that are suitable for studying the pathogenesis of this disease, preclinical studies of the specific activity and harmlessness of candidate vaccines, as well as options for these developments based on the platforms such as inactivated LASV and its DNA, the reassortant of Mopeia arenavirus, and measles virus attenuated strains, recombinant and replication-defective viruses (smallpox vaccine, Venezuelan equine encephalitis, bovine vesicular stomatitis, adenovirus of chimpanzee) and virus-like particles.

Presently, the Arenavirus genus (Arenaviridae family) includes 26 individual species of viruses. It is divided into two main groups – Old World arenaviruses and New World arenaviruses. The New World arenaviruses comprise four clades: А, B, C, D; pathogenic for humans New World arenaviruses are attributed to clade B. Lassa, Lujo, Machupo, Junin, Guanarito and Sabia viruses are the agents of extremely hazardous hemorrhagic fevers (Lassa hemorrhagic fever, Lujo hemorrhagic fever, Bolivian hemorrhagic fever, Argentinean hemorrhagic fever, Venezuelan hemorrhagic fever, Brazilian hemorrhagic fever, accordingly). These arenaviruses pose a potential threat to national public health due to the possibility of their accidental importation into the territory of the Russian Federation. The vaccination of risk group is the most effective and money-saving means of protection against epidemic spread. Objective of this review is to analyze the specific preparations for arenaviral hemorrhagic fever prevention that are currently under development. Production of live vaccines based on attenuated strains of the agents, the DNA vaccines, vector recombinant vaccines and vaccines on the basis of RNA-replicons is viewed as the main trends in the area. Тhe most important results in the development of effective prophylactic means against arenaviral hemorrhagic fevers are discussed in this paper.