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Encyclopedia > Lassa fever
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Lassa virus
Virus classification
Group: Group V ((-)ssRNA)
Family: Arenaviridae
Genus: Arenavirus
Species: Lassa virus
Lassa fever
ICD-10 A962
ICD-9 078.8
DiseasesDB 7272

Lassa fever is an acute viral hemorrhagic fever first described in 1969 in the Nigerian town of Lassa in the Yedseram River valley. Clinical cases of the disease had been known for over a decade earlier but not connected with this viral pathogen.
The infection is endemic in West African countries, causing many deaths. Outbreaks of the disease have been observed in the following countries: Viruses can be classified in several ways, such as by their geometry, by whether they have envelopes, by the identity of the host organism they can infect, by mode of transmission, or by the type of disease they cause. ... An RNA virus is a virus that either uses RNA as its genetic material, or whose genetic material passes through an RNA intermediate during replication. ... Arenavirus is a genus of virus. ... Arenavirus is a genus of virus. ... The following codes are used with International Statistical Classification of Diseases and Related Health Problems. ... // A00-A79 - Bacterial infections, and other intestinal infectious diseases, and STDs (A00-A09) Intestinal infectious diseases (A00) Cholera (A01) Typhoid and paratyphoid fevers (A010) Typhoid fever (A02) Other Salmonella infections (A03) Shigellosis (A04) Other bacterial intestinal infections (A040) Enteropathogenic Escherichia coli infection (A045) Campylobacter enteritis (A046) Enteritis due to Yersinia... The following is a list of codes for International Statistical Classification of Diseases and Related Health Problems. ... The Diseases Database is a free website that provides information about the relationships between medical conditions, symptoms, and medications. ... The human immunodeficiency virus (HIV) A bacteriophage virus A virus is a submicroscopic parasitic particle that infects cells in biological organisms. ... Viral hemorrhagic fevers are a group of illnesses that are caused by several distinct families of viruses: Arenavirus, Filoviridae, Bunyaviridae and Flavivirus. ... In epidemiology, an infection is said to be endemic in a population when that infection is maintained in the population without the need for external inputs. ... Africa is the worlds second-largest and second-most populous continent, after Asia. ...

but it is believed that human infections also exist in:

It is also the most common hemorrhagic fever that is exported beyond its endemic area to countries like the United States, United Kingdom, The Netherlands, Japan and Israel.

Contents


The virus and epidemiology

The virus belongs to Arenaviridae family; it is an enveloped, single-stranded, bisegmented RNA virus. It has been determined that the virus is zoonotic (transmitted from animals), and that it spreads to man from rodents, specifically multimammate rats (Mastomys natalensis). This is probably the most common rodent in equatorial Africa, ubiquitous in human households and eaten as a delicacy by up to 90% of people in some areas. In these rats infection is in a persistent asymptomatic state. The virus is shed in their excreta (urine and feces), which can be aerosolized. Arenavirus is a genus of virus. ... Ribonucleic acid (RNA) is a nucleic acid polymer consisting of covalently bound nucleotides. ... Zoonosis (pronounced as zoo-on-no-sis) is any infectious disease that may be transmitted from animals, both wild and domestic, to humans. ... Families See Classification Section The order Rodentia is the most numerous of the branches on the mammal family tree. ...


In fatal cases Lassa fever is characterized by impaired or delayed cellular immunity leading to fulminant viraemia.


The dissemination of the infection can be assessed by prevalence of antibodies to the virus in populations of:

  • Sierra Leone 8–52%
  • Guinea 4–55%
  • Nigeria approx. 21%

Like other hemorrhagic fevers, Lassa fever can be transmitted directly from one human to another. It can be contracted by an airborne route or with direct contact with infected human blood, urine, or semen. Transmission through breast milk has also been observed.


Lassa fever is less deadly compared to ebola, though they share similar symptoms. Because Lassa is a very fast replicating and debilitating virus, the chances of a worldwide epidemic are small. Patients are far too weak to board a plane and spread it to other parts of the world.


Lassa fever is a virus that has emerged relatively recently. It has managed to appear in a relatively short span of history. Because Lassa fever has a reservoir (rodents), it is difficult to eliminate.


The disease

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. Transmission from person to person has also been established, presenting a disease risk for healthcare workers. Frequency of transmission via sexual contact has not been established. In humans the respiratory tract is the part of the anatomy that has to do with the process of respiration or breathing. ... The gastrointestinal tract or digestive tract, also referred to as the GI tract or the alimentary canal or the gut, is the system of organs within multicellular animals which takes in food, digests it to extract energy and nutrients, and expels the remaining waste. ... A section of Human Skin In zootomy and dermatology, skin is an organ of the integumentary system made up of a layer of tissues that guard underlying muscles and organs. ... The mucous membranes (or mucosae; singular: mucosa) are linings of ectodermic origin, covered in epithelium, and are involved in absorption and secretion. ...


In 80% of cases the disease is inapparent, but in the remaining 20% it takes a complicated course. It is estimated that the virus is responsible for about 5,000 deaths annually. The fever accounts for up to 1/3 of deaths in hospitals within the affected regions and 10 to 16% of total cases.


After an incubation period of six to twenty-one days, an acute illness with multiorgan involvement develops. Nonspecific symptoms include fever, facial swelling, and muscle fatigue, as well as conjunctivitis and mucosal bleeding. The other symptoms arising from the affected organs are: Incubation period is the time elapsed between exposure to a pathogenic organism and when symptoms and signs are first apparent. ... See Fever for the Kylie Minogue album; Fever is also a song by Otis Blackwell. ...

Clinically, Lassa fever infections are difficult to distinguish from other viral hemorrhagic fevers such as Ebola, and from more commom febrile illnesses such as malaria. The gastrointestinal tract or digestive tract, also referred to as the GI tract or the alimentary canal or the gut, is the system of organs within multicellular animals which takes in food, digests it to extract energy and nutrients, and expels the remaining waste. ... For other uses, see Nausea (disambiguation). ... Vomiting (or emesis) is the forceful expulsion of the contents of ones stomach through the mouth. ... Diarrhea or diarrhoea (see spelling differences) is a condition in which the sufferer has frequent loose bowel movements (from the ancient Greek word διαρροή = leakage; lit. ... Stomach ache is a non-medical term used to describe various forms of nausea or abdominal pain. ... Constipation or Irregularity, is a condition of the digestive system where a person (or animal) experiences hard feces that are difficult to eliminate; it may be extremely painful, and in severe cases (fecal impaction) lead to symptoms of bowel obstruction. ... Dysphagia is the technical term for the symptom of the sensation of difficulty in swallowing. ... Hepatitis is a gastroenterological disease, featuring inflammation of the liver. ... The circulatory system or cardiovascular system is the organ system which circulates blood around the body of most animals. ... Pericarditis is inflammation of the pericardium. ... For other forms of hypertension see hypertension (disambiguation). ... In physiology and medicine, hypotension refers to an abnormally low blood pressure. ... Tachycardia is an abnormally rapid beating of the heart, defined as a resting heart rate of 100 or more beats per minute in an average adult. ... In humans the respiratory tract is the part of the anatomy that has to do with the process of respiration or breathing. ... Dyspnea (Latin dyspnoea, Greek dyspnoia from dyspnoos - short of breath) or shortness of breath (SOB) is perceived difficulty breathing or pain on breathing. ... Pharyngitis is a painful inflammation of the pharynx, and is colloquially referred to as a sore throat. ... ... The nervous system of an animal coordinates the activity of the muscles, monitors the organs, constructs and also stops input from the senses, and initiates actions. ... Encephalitis is an acute inflammation of the brain, commonly caused by a viral infection. ... Meningitis is inflammation of the membranes (meninges) covering the brain and the spinal cord. ... This article is about the medical term, epileptic seizure, as distinct from psychogenic non-epileptic seizure. ... Species Ivory Coast ebolavirus Reston ebolavirus Sudan ebolavirus Zaire ebolavirus Ebola is a virus of the Filoviridae family which causes Ebola hemorrhagic fever, a fatal disease in humans. ... Red blood cell infected with Malaria, derived from mala aria (Medieval Italian for bad air) and formerly called ague or marsh fever in English, is an infectious disease which causes about 350-500 million infections with humans and approximately 1. ...


The virus is excreted in urine for three to nine weeks and in semen for three months.


Virus 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 mRNA copies of the - sense genome. This ensures that there is adequate proteins, which are required for replication. The N and L proteins are made from the mRNA produced. The - sense genome then makes vcRNA copies of itself which are + sense. The vcRNA is a template for producing - sense progeny but mRNA is also synthesised from it. The mRNA synthesised from vcRNA translate the 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 immune system.


Lassa virus will infect just about every tissue in the human body. It starts with the mucosa, intestine, lungs and urinary systems, and then progresses to the vascular system.


Lab tests

There is a range of laboratory investigations that are performed to diagnose the disease and assess its course and complications. ELISA test for antigen and IgM antibodies gives 88% sensitivity and 90% specificity for the presence of the infection. Other laboratory findings in Lassa fever:

Lymphopenia is the condition in which there exists an abnormally low number of lymphocytes in the blood. ... Thrombocytopenia (or -paenia, or thrombopenia in short) is the presence of relatively few platelets in blood. ... Aspartate transaminase (AST) also called Serum Glutamic Oxaloacetic Transaminase (SGOT) or aspartate aminotransferase (ASAT) (EC 2. ...

Prevention

Control of the Mastomys rodent population is impractical, so measures are limited to keeping rodents out of homes and food supplies, as well as maintaining effective personal hygiene. Gloves, masks, laboratory coats, and goggles are advised while in contact with an infected person.


No vaccine against Lassa fever is currently available, though development is underway. The Mozambique virus closely resembles Lassa fever, while lacking its deadly effects. This virus is being considered for possible use as a vaccine. A vaccine is an antigenic preparation used to produce active immunity to a disease, in order to prevent or ameliorate the effects of infection by any natural or wild strain of the organism. ...


Researchers at the USAMRIID facility, where military biologists study infectious diseases, have a promising vaccine candidate3. They have developed a replication-competent vaccine against Lassa virus based on recombinant vesicular stomatitis virus vectors expressing the Lassa virus glycoprotein. After a single intramuscular injection, test primates have survived leathal challenge, while showing no clinical symptoms. 2 The U.S. Army Medical Research Institute of Infectious Diseases is based at Fort Detrick, Frederick, Maryland. ... The human immunodeficiency virus (HIV) A bacteriophage virus A virus is a submicroscopic parasitic particle that infects cells in biological organisms. ... Stomatitis is an inflammation of the mucous lining of any of the structures in the mouth, which may involve the cheeks, gums, tongue, lips, and roof or floor of the mouth. ... Vesicular stomatitis virus (VSV) is a virus in the family Rhabdoviridae, order Mononegavirales. ... Intramuscular injection is an injection of a substance directly into a muscle. ...


Treatment

All persons suspected of Lassa fever infection should be admitted to isolation facilities and their body fluids and excreta properly disposed of.


Early and aggressive treatment using ribavirin was pioneered by Joe McCormick in 1979. After extensive testing, it was determined that early administration is critical to success. Additionally, ribavirin is almost twice as effective when given intravenously as when taken by mouth. The drug interferes with the virus metabolism, inhibiting its replication. The drug is relatively inexpensive, but the cost of the drug is still very high for many of those in poverty-stricken West African states. Fluid replacement, blood transfusion and fighting hypotension are usually required. Ribavirin (Copegus®; Rebetol®; Ribasphere®; Vilona®,Virazole®, also generics from Sandoz, Teva, Warrick) is an anti-viral drug which is active against a number of DNA and RNA viruses. ... This article or section does not cite its references or sources. ... Santorio Santorio (1561-1636) in his steelyard balance, from Ars de statica medecina, first published 1614 Metabolism (from μεταβολισμος (metabolismos)) is the biochemical modification of chemical compounds in living organisms anggjgjhnd cell (b). ... Replication may mean: In biology: Self-replication, when a molecule (or any other pattern) makes a copy of itself DNA replication, the act of copying the genetic material of a cell (DNA) to a daughter cell Semiconservative replication, mechanism of DNA replication Other: replication (computer science), the provision of redundant...


Prognosis

About 15%-20% of hospitalized Lassa fever patients will die from the illness. It is estimated that the overall mortality rate is 1%, however during epidemics mortality can climb as high as 50%. Thanks to treatment with ribavirin, fatality rates are continuing to decline. Work on a vaccine is continuing, with multiple approaches showing positive results in animal trials. In epidemiology, an epidemic (from Greek epi- upon + demos people) is a disease that appears as new cases in a given human population, during a given period, at a rate that substantially exceeds what is expected, based on recent experience (the number of new cases in the population during a... Ribavirin (Copegus®; Rebetol®; Ribasphere®; Vilona®,Virazole®, also generics from Sandoz, Teva, Warrick) is an anti-viral drug which is active against a number of DNA and RNA viruses. ...


Lassa fever virus as a biological weapon

The terrorist attack on 11 September 2001 and threat of biological warfare attack alerted governmental agencies and scientists. Lassa fever virus is also regarded as a possible biological weapon. The explosion resulting from the crashing of United Airlines Flight 175 into the South Tower. ... September 11 is the 254th day of the year in the Gregorian calendar (255th in leap years). ... 2001: A Space Odyssey. ... Biological warfare, also known as germ warfare, is the use of any organism (bacteria, virus or other disease_causing organism) or toxin found in nature, as a weapon of war. ...


References

  • Theiler, Max and Downs, W. G. 1973. The Arthropod-Borne Viruses of Vertebrates: An Account of The Rockefeller Foundation Virus Program 1951-1970. Yale University Press.
  • Note 2: Geisbert TW, Jones S, Fritz EA, Jahrling P, et al. 2005 Development of a new vaccine for the prevention of lassa fever. PLOS MEDICINE 2 (6): 537-545 JUN 2005.
  • Dato-on, Airam. 2006 Lassa Fever Research Paper.

PLoS Medicine is a scientific journal covering the full spectrum of the medical sciences it began operation on October 19, 2004. ... Richard Preston (b. ...

External links

  • Centers for Disease Control
  • WHO factsheet
  • CDC info - viral fevers
  • Health Protection Agency - viral haemorrhagic fevers
  • Merlin

  Results from FactBites:
 
Lassa fever - Wikipedia, the free encyclopedia (1163 words)
Lassa fever is an acute viral hemorrhagic fever first described in 1969 in the Nigerian town of Lassa in the Yedseram River valley.
Lassa fever is less deadly compared to ebola, though they share similar symptoms.
Clinically, Lassa fever infections are difficult to distinguish from other viral hemorrhagic fevers such as Ebola, and from more commom febrile illnesses such as malaria.
Lassa Fever | CDC Special Pathogens Branch (1214 words)
Lassa fever is an acute viral illness that occurs in West Africa.
In areas of Africa where the disease is endemic (that is, constantly present), Lassa fever is a significant cause of morbidity and mortality.
Lassa fever is an endemic disease in portions of West Africa.
  More results at FactBites »

 
 

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