Re-emergence of Lassa fever in Nigeria: A new challenge for public health authorities.

The Lassa virus is an RNA virus belonging to the Arenaviridae family. It is responsible for Lassa fever, an acute viral zoonosis of the severe hemorrhagic fever type with manifestations of fever, muscle pain, sore throat, nausea, vomiting, and chest and abdominal pain. Lassa fever is endemic in West Africa, where the first case was reported in 1969 in Lassa, a town in Nigeria, more than 50 years ago, and it is estimated that nearly 5000 deaths occur in West Africa each year. Nigeria is one of the endemic hotspots and has experienced numerous recurrent outbreaks of Lassa fever due to the increased multiplication of the host reservoir, Mastomys natalensis . For the Lassa epidemics in 2022 and January 2023 alone, Nigeria accounts for a quarter of the annual deaths from this disease. Poor lifestyle and hygiene, difficulty in diagnosis due to nonspecific symptomatology, lack of effective treatment based on clinical evidence, an ineffective human immunization program combined with a health system that is not adapted or equipped to control and prevent recurrent deadly epidemics, and an outdated regional disease surveillance system in West Africa are some of the challenges that must be overcome to rapidly and effectively eradicate this disease, whose area of spread is constantly expanding as a result of the movement of populations in the context of economic and socio-cultural activities.