Lassa Fever: An acute febrile human disease caused by the LASSA VIRUS.Lassa virus: A species of ARENAVIRUS, part of the Old World Arenaviruses (ARENAVIRUSES, OLD WORLD), and the etiologic agent of LASSA FEVER. LASSA VIRUS is a common infective agent in humans in West Africa. Its natural host is the multimammate mouse Mastomys natalensis.Arenaviridae: A family of RNA viruses naturally infecting rodents and consisting of one genus (ARENAVIRUS) with two groups: Old World Arenaviruses (ARENAVIRUSES, OLD WORLD) and New World Arenaviruses (ARENAVIRUSES, NEW WORLD). Infection in rodents is persistent and silent. Vertical transmission is through milk-, saliva-, or urine-borne routes. Horizontal transmission to humans, monkeys, and other animals is important.Africa, Western: The geographical area of Africa comprising BENIN; BURKINA FASO; COTE D'IVOIRE; GAMBIA; GHANA; GUINEA; GUINEA-BISSAU; LIBERIA; MALI; MAURITANIA; NIGER; NIGERIA; SENEGAL; SIERRA LEONE; and TOGO.Patient Isolators: Equipment used to prevent contamination of and by patients, especially those with bacterial infections. This includes plastic surgical isolators and isolators used to protect immunocompromised patients.Fever: An abnormal elevation of body temperature, usually as a result of a pathologic process.Murinae: A subfamily in the family MURIDAE, comprising the Old World MICE and RATS.Arenavirus: The only genus in the family ARENAVIRIDAE. It contains two groups ARENAVIRUSES, OLD WORLD and ARENAVIRUSES, NEW WORLD, which are distinguished by antigenic relationships and geographic distribution.Guinea: A republic in western Africa, south of SENEGAL and MALI, east of GUINEA-BISSAU. Its capital is Conakry.Arenaviridae Infections: Virus diseases caused by the ARENAVIRIDAE.Pichinde virus: A species of ARENAVIRUS, one of the New World Arenaviruses (ARENAVIRUSES, NEW WORLD), causing a fatal infection in the cricetine rodent Oryzomys albigularis. Asymptomatic laboratory infection in humans has been reported.Hemorrhagic Fevers, Viral: A group of viral diseases of diverse etiology but having many similar clinical characteristics; increased capillary permeability, leukopenia, and thrombocytopenia are common to all. Hemorrhagic fevers are characterized by sudden onset, fever, headache, generalized myalgia, backache, conjunctivitis, and severe prostration, followed by various hemorrhagic symptoms. Hemorrhagic fever with kidney involvement is HEMORRHAGIC FEVER WITH RENAL SYNDROME.Liberia: A republic in western Africa, south of GUINEA and east of COTE D'IVOIRE. Its capital is Monrovia.Arenaviruses, Old World: One of two groups of viruses in the ARENAVIRUS genus and considered part of the Old World complex. It includes LASSA VIRUS and LYMPHOCYTIC CHORIOMENINGITIS VIRUS, although the latter has worldwide distribution now.Arenaviruses, New World: One of two groups of viruses in the ARENAVIRUS genus and considered part of the New World complex. It includes JUNIN VIRUS; PICHINDE VIRUS; Amapari virus, and Machupo virus among others. They are the cause of human hemorrhagic fevers mostly in Central and South America.Marburg Virus Disease: An RNA virus infection of rhesus, vervet, and squirrel monkeys transmissible to man.Missions and Missionaries: To be used for articles pertaining to medical activities carried out by personnel in institutions which are administered by a religious organization.Disease Reservoirs: Animate or inanimate sources which normally harbor disease-causing organisms and thus serve as potential sources of disease outbreaks. Reservoirs are distinguished from vectors (DISEASE VECTORS) and carriers, which are agents of disease transmission rather than continuing sources of potential disease outbreaks.Q Fever: An acute infectious disease caused by COXIELLA BURNETII. It is characterized by a sudden onset of FEVER; HEADACHE; malaise; and weakness. In humans, it is commonly contracted by inhalation of infected dusts derived from infected domestic animals (ANIMALS, DOMESTIC).RNA Viruses: Viruses whose genetic material is RNA.Nigeria: A republic in western Africa, south of NIGER between BENIN and CAMEROON. Its capital is Abuja.Yellow Fever: An acute infectious disease primarily of the tropics, caused by a virus and transmitted to man by mosquitoes of the genera Aedes and Haemagogus. The severe form is characterized by fever, HEMOLYTIC JAUNDICE, and renal damage.Sierra Leone: A republic in western Africa, south of GUINEA and west of LIBERIA. Its capital is Freetown.Typhoid Fever: An acute systemic febrile infection caused by SALMONELLA TYPHI, a serotype of SALMONELLA ENTERICA.Lymphocytic choriomeningitis virus: The type species of ARENAVIRUS, part of the Old World Arenaviruses (ARENAVIRUSES, OLD WORLD), producing a silent infection in house and laboratory mice. In humans, infection with LCMV can be inapparent, or can present with an influenza-like illness, a benign aseptic meningitis, or a severe meningoencephalomyelitis. The virus can also infect monkeys, dogs, field mice, guinea pigs, and hamsters, the latter an epidemiologically important host.Virus Diseases: A general term for diseases produced by viruses.Dystroglycans: Dystrophin-associated proteins that play role in the formation of a transmembrane link between laminin-2 and DYSTROPHIN. Both the alpha and the beta subtypes of dystroglycan originate via POST-TRANSLATIONAL PROTEIN PROCESSING of a single precursor protein.Antibodies, Viral: Immunoglobulins produced in response to VIRAL ANTIGENS.Viremia: The presence of viruses in the blood.