Lassa fever pathophysiology: Difference between revisions
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==Pathophysiology== | ==Pathophysiology== | ||
Lassa virus is [[zoonosis|zoonotic]] (transmitted from animals). The [[natural reservoir|reservoir]], or [[definitive host|host]], of Lassa virus is a rodent known as the "multimammate rat" of the genus Mastomys. It is not certain which species of Mastomys are associated with Lassa; however, at least two species carry the virus in Sierra Leone. Mastomys | Lassa virus is [[zoonosis|zoonotic]] ([[transmission|transmitted]] from animals). The [[natural reservoir|reservoir]], or [[definitive host|host]], of Lassa virus is a rodent known as the "multimammate rat" of the [[genus]] Mastomys. It is not certain which [[species]] of Mastomys are associated with Lassa; however, at least two species carry the virus in Sierra Leone. Mastomys [[rodent]]s breed very frequently, produce large numbers of [[offspring]], and are numerous in the savannas and forests of West, Central, and East Africa. In addition, Mastomys generally readily colonize human homes. All these factors together contribute to the relatively efficient spread of Lassa virus from infected rodents to humans. | ||
===Transmission=== | ===Transmission=== | ||
Infection in humans typically occurs via exposure to animal [[excretion|excrement]] through the [[respiratory tract|respiratory]] or [[gastrointestinal tract|gastrointestinal]] tracts. [[Inhalation]] of tiny particles of infective material ([[aerosol]]) is believed to be the most significant means of exposure. It is possible to acquire the [[infection]] through broken [[skin]] or [[mucous membrane]]s that are directly exposed to infective material. In fatal cases, Lassa fever is characterized by impaired or delayed [[cellular immunity]] leading to [[fulminant]] [[viremia]]. | |||
Lassa fever may also spread through person-to-person contact. This type of transmission occurs when a person comes into contact with virus in the blood, tissue, [[secretion]]s, or [[excretion]]s of an individual infected with the Lassa virus. The virus cannot be spread through casual contact (including skin-to-skin contact without exchange of body fluids). Person-to-person transmission is common in both village and health care settings, where, along with the above-mentioned modes of transmission, the virus also may be spread in contaminated medical equipment, such as reused needles (this is called [[nosocomial]] [[transmission]]). Frequency of transmission via sexual contact has not been established. Transmission through [[breast milk]] has also been observed. | There are a number of ways in which the virus may be transmitted, or spread, to humans. The Mastomys rodents shed the virus in [[urine]] and droppings. Therefore, the virus can be transmitted through direct contact with these materials, through touching objects or eating food [[contamination|contaminated]] with these materials, or through cuts or [[sore]]s. Because Mastomys rodents often live in and around homes and scavenge on human food remains or poorly stored food, transmission of this sort is common. Contact with the virus also may occur when a person inhales tiny particles in the air contaminated with rodent excretions. This is called [[aerosol]] or [[airborne transmission]]. Finally, because Mastomys rodents are sometimes consumed as a food source, [[infection]] may occur via direct contact when they are caught and prepared for food. | ||
Lassa fever may also spread through person-to-person contact. This type of transmission occurs when a person comes into contact with virus in the [[blood]], [[tissue]], [[secretion]]s, or [[excretion]]s of an individual infected with the Lassa virus. The virus cannot be spread through casual contact (including skin-to-skin contact without exchange of [[body fluids]]). Person-to-person transmission is common in both village and health care settings, where, along with the above-mentioned modes of transmission, the virus also may be spread in contaminated medical equipment, such as reused needles (this is called [[nosocomial]] [[transmission]]). Frequency of transmission via sexual contact has not been established. Transmission through [[breast milk]] has also been observed. | |||
==References== | ==References== | ||
Revision as of 13:51, 24 December 2012
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Pathophysiology
Lassa virus is zoonotic (transmitted from animals). The reservoir, or host, of Lassa virus is a rodent known as the "multimammate rat" of the genus Mastomys. It is not certain which species of Mastomys are associated with Lassa; however, at least two species carry the virus in Sierra Leone. Mastomys rodents breed very frequently, produce large numbers of offspring, and are numerous in the savannas and forests of West, Central, and East Africa. In addition, Mastomys generally readily colonize human homes. All these factors together contribute to the relatively efficient spread of Lassa virus from infected rodents to humans.
Transmission
Infection in humans typically occurs via exposure to animal excrement through the respiratory or gastrointestinal tracts. Inhalation of tiny particles of infective material (aerosol) is believed to be the most significant means of exposure. It is possible to acquire the infection through broken skin or mucous membranes that are directly exposed to infective material. In fatal cases, Lassa fever is characterized by impaired or delayed cellular immunity leading to fulminant viremia.
There are a number of ways in which the virus may be transmitted, or spread, to humans. The Mastomys rodents shed the virus in urine and droppings. Therefore, the virus can be transmitted through direct contact with these materials, through touching objects or eating food contaminated with these materials, or through cuts or sores. Because Mastomys rodents often live in and around homes and scavenge on human food remains or poorly stored food, transmission of this sort is common. Contact with the virus also may occur when a person inhales tiny particles in the air contaminated with rodent excretions. This is called aerosol or airborne transmission. Finally, because Mastomys rodents are sometimes consumed as a food source, infection may occur via direct contact when they are caught and prepared for food.
Lassa fever may also spread through person-to-person contact. This type of transmission occurs when a person comes into contact with virus in the blood, tissue, secretions, or excretions of an individual infected with the Lassa virus. The virus cannot be spread through casual contact (including skin-to-skin contact without exchange of body fluids). Person-to-person transmission is common in both village and health care settings, where, along with the above-mentioned modes of transmission, the virus also may be spread in contaminated medical equipment, such as reused needles (this is called nosocomial transmission). Frequency of transmission via sexual contact has not been established. Transmission through breast milk has also been observed.