Arenaviridae

An arenavirus is a negative-sense, single-stranded RNA virus that is a member of the family Arenaviridae. These viruses infect rodents and occasionally humans; arenaviruses have also been discovered which infect snakes. At least eight arenaviruses are known to cause human disease. The diseases derived from arenaviruses range in severity. Aseptic meningitis, a severe human disease that causes inflammation covering the brain and spinal cord, can arise from the lymphocytic choriomeningitis virus (LCMV) infection. Hemorrhagic fever syndromes, including Lassa fever, are derived from infections such as Guanarito virus (GTOV), Junin virus (JUNV), Lassa virus (LASV), Lujo virus (LUJV), Machupo virus (MACV), Sabia virus (SABV), or Whitewater Arroyo virus (WWAV). Arenaviruses are divided into two groups: the Old World and the New World viruses. The differences between these groups are distinguished geographically and genetically. Because of the epidemiological association with rodents, some arenaviruses and bunyaviruses are designated as roboviruses. Viewed in cross-section, arenaviruses contain grainy particles that are ribosomes acquired from their host cells. It is from this characteristic that they acquired the name arena, from the Latin root meaning sand. The ribosomal structures are not believed to be essential for virus replication. Virus particles, or virions, are pleomorphic (variable in shape) but are often spherical, with a diameter of 60–300 nm, and are covered with surface glycoprotein spikes. The virus contains a beaded nucleocapsid with two single-stranded RNA segments. The nucleocapsid consists of a core of nucleic acid enclosed in a protein coat. Although they are categorized as negative-sense viruses, arenaviruses are ambisense. While sections of their genome encode genes in the negative sense (reverse polarity), other sections encode genes in the opposite (forward/positive sense) direction. This complex gene expression structure is theorized to be a primitive regulatory system, allowing the virus to control what proteins are synthesized at what point in the life cycle. The life cycle of the arenavirus is restricted to the cell cytoplasm. Within the family Arenaviridae, arenaviruses were formerly all placed in the genus Arenavirus, but were recently (2014) reclassified into the genera Mammarenavirus for those with mammalian hosts and Reptarenavirus for those infecting snakes. A third genus - Hartmanivirus - has also been established. Species in the Hartmanivirus also infect snakes. The organisation of the genome of this genus is typical of arenaviruses but their glycoproteins resemble those of filoviruses. Species in this genus lack the matrix protein. An arenavirus - Wenling frogfish arenavirus - has been described in fish. Its classification has yet to be decided. Arenaviruses can be divided into two serogroups, which differ genetically and by geographical distribution:When the virus is classified “Old World” this means it was found in the Eastern Hemisphere in places such as Europe, Asia, and Africa. When it is found in the Western Hemisphere, in places such as Argentina, Bolivia, Venezuela, Brazil, and the United States, it is classified “New World”. Lymphocytic choriomeningitis (LCM) virus is the only arenavirus to exist in both areas but is classified as an Old World virus. Old and New World area viruses appear to have diverged ~45,000 years ago. The Old World mammarenaviruses originated ∼23.1-1.88 thousand years ago, most likely in Southern Africa while the New World mammarenaviruses evolved in the Latin America-Caribbean region ∼41.4-3.3 thousand years ago