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| __NOTOC__
| | #redirect [[Lassa virus]] |
| {{Lassa fever}}
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| {{CMG}}; {{AE}} {{Ammu}}
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| ==Overview==
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| Lassa fever is caused by the ''Lassa virus'', a member of the [[Arenaviridae]] family; it is an [[enveloped virus|enveloped]], single-stranded, bisegmented [[RNA]] virus. [[viral replication|Replication]] for Lassa virus is very rapid, while also demonstrating temporal control in replication. There are two [[genome]] segments. The first step involved is making [[messenger RNA|mRNA]] copies of the negative-sense [[genome]]. This ensures that there are adequate [[protein]]s, which are required for [[replication]]. The N and L proteins are made from the mRNA produced. The -ve sense genome then makes vcRNA (viral circular RNA) copies of itself which are positive-sense. The vcRNA is a [[template strand|template]] for producing -ve sense progeny but mRNA is also synthesized from it. The mRNA synthesized from vcRNA [[translation (biology)|translates]] the [[G proteins|G (spike) proteins]] and Z proteins. Thus, with this temporal control, the spike proteins are produced last, making the infection further undetected by the [[host (biology)|host]] [[immune system]].
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| ==Virus==
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| * Lassa virus belongs to Arenaviridae.
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| * The Arenaviridae are a family of [[viruses]] whose members are generally associated with rodent-transmitted diseases in [[humans]]. Each [[virus]] usually is associated with a particular [[rodent]] host species in which it is maintained. [[Arenavirus]] infections are relatively common in humans in some areas of the world and can cause severe [[illnesses]].
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| * The virus particles are spherical and have an average diameter of 110-130 nanometers. All are enveloped in a [[lipid]] (fat) membrane. Viewed in cross-section, they show grainy particles that are [[ribosomes]] acquired from their [[host]] cells. It is this characteristic that gave them their name, derived from the Latin "arena", which means "sandy". Their genome, or genetic material, is composed of [[RNA]] only, and while their replication strategy is not completely understood, we know that new viral particles, called [[virions]], are created by budding from the surface of their [[hosts]]' cells.
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| [[File:Lassa fever micro.png|thumb|center|400 px|Outbreak Distribution Map Lassa Fever CDC.png<SMALL><SMALL>''[http://www.cdc.gov/vhf/virus-families/arenaviridae.html]''<ref name="CDC">{{Cite web | title = Center for Disease Control and Prevention (CDC) | url = http://www.cdc.gov}}</ref></SMALL></SMALL>]]
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| ===History of Arenaviridae===
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| * The first Arenavirus, Lymphocytic choriomeningitis virus (LCMV), was isolated in 1933 during a study of an epidemic of St. Louis encephalitis. Although not the cause of the outbreak, LCMV was found to be a cause of aseptic (nonbacterial) meningitis. By the 1960s, several similar viruses had been discovered and they were classified into the new family Arenaviridae. Since Tacaribe virus was found in 1956, new Arenavirus have been discovered on the average of every one to three years. A number of Arenavirus have been isolated in rodents only, but few cause hemorrhagic disease. Junin virus, isolated in 1958, was the first of these to be recognized. This virus causes Argentine hemorrhagic fever in a limited agrigultural area of the pampas in Argentina. Several years later, in 1963, in the remote savannas of the Beni province of Bolivia, Machupo virus was isolated. The next member of the virus family to be associated with an outbreak of human illness was Lassa virus in Nigeria in 1969. The most recent additions to these human pathogenic viruses were Guanarito detected in Venezuela in 1989, Sabia in Brazil in 1993, Chapare in Bolivia in 2004, and Lujo in South Africa in 2008.
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| ==Vector==
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| * The reservoir, or host, of Lassa virus is a rodent known as the "multimammate rat" (Mastomys natalensis). Once infected, this rodent is able to excrete [[virus]] in [[urine]] for an extended time period, maybe for the rest of its life. Mastomys rodents breed frequently, produce large numbers of offspring, and are numerous in the savannas and forests of west, central, and east Africa. In addition, Mastomys readily colonize human homes and areas where food is stored. All of these factors contribute to the relatively efficient spread of Lassa virus from infected rodents to humans.
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| * Transmission of Lassa virus to humans occurs most commonly through [[ingestion]] or [[inhalation]]. Mastomysrodents shed the [[virus]] in [[urine]] and droppings and direct contact with these materials, through touching soiled objects, eating contaminated food, or exposure to open cuts or sores, can lead to [[infection]].
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| * Because Mastomys rodents often live in and around homes and scavenge on leftover human food items or poorly stored food, direct contact transmission is common. Mastomys rodents are sometimes consumed as a food source and infection may occur when rodents are caught and prepared. Contact with the [[virus]] may also occur when a person inhales tiny particles in the air contaminated with infected rodent excretions. This aerosol or airborne transmission may occur during cleaning activities, such as sweeping.
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| * Direct contact with infected rodents is not the only way in which people are infected; person-to-person transmission may occur after exposure to [[virus]] in the [[blood]], [[tissue]], secretions, or excretions of a Lassa virus-infected individual. Casual contact (including [[skin]]-to-[[skin]] contact without exchange of [[body fluids]]) does not spread Lassa virus. Person-to-person transmission is common in health care settings (called [[nosocomial transmission]]) where proper personal protective equipment (PPE) is not available or not used. Lassa virus may be spread in contaminated medical equipment, such as reused needles.
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| ==References==
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| {{Reflist|2}}
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| [[Category:Disease]]
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| [[Category:Viral diseases]]
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| [[Category:Hemorrhagic fevers]]
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| [[Category:Tropical disease]]
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