Originally posted by NLion at 28-4-2009 01:56
heard its in UK now, but does anyone know exactly how it originated?
taken from
http://en.wikipedia.org/wiki/Swine_flu
Swine influenza virus (referred to as SIV) refers to influenza cases that are caused by Orthomyxoviruses that are endemic to pig populations. SIV strains isolated to date have been classified either as Influenzavirus C or one of the various subtypes of the genus Influenzavirus A.[1]
Swine flu can mutate into a form that allows it to pass from human to human. The strain responsible for the 2009 swine flu outbreak is believed to have undergone this mutation.[2]
Swine influenza is known to be caused by influenza A subtypes H1N1,[3] H1N2,[3] H3N1,[4] H3N2,[3] and H2N3.[5]
In swine, three influenza A virus subtypes (H1N1, H3N2, and H1N2) are circulating throughout the world. In the United States, the H1N1 subtype was exclusively prevalent among swine populations before 1998; however, since late August 1998, H3N2 subtypes have been isolated from pigs. As of 2004, H3N2 virus isolates in US swine and turkey stocks were triple reassortants, containing genes from human (HA, NA, and PB1), swine (NS, NP, and M), and avian (PB2 and PA) lineages
Causes
H5N1
Avian influenza virus H3N2 is endemic in pigs in China and has been detected in pigs in Vietnam, increasing fears of the emergence of new variant strains.[10] Health experts[who?] say pigs can carry human influenza viruses, which can combine (i.e. exchange homologous genome sub-units by genetic reassortment) with H5N1, passing genes and mutating into a form which can pass easily among humans.[11] H3N2 evolved from H2N2 by antigenic shift.[12] In August 2004, researchers in China found H5N1 in pigs.[13]
Nature magazine reported that Chairul Nidom, a virologist at Airlangga University's tropical disease center in Surabaya, East Java, conducted an independent research study in 2005. He tested the blood of 10 apparently healthy pigs housed near poultry farms in West Java where avian flu had broken out. Five of the pig samples contained the H5N1 virus. The Indonesian government has since found similar results in the same region. Additional tests of 150 pigs outside the area were negative.[14][15]
Swine flu in humans
People who work with poultry and swine, especially people with intense exposures, are at increased risk of zoonotic infection with influenza virus endemic in these animals, and constitute a population of human hosts in which zoonosis and reassortment can co-occur.[17] Transmission of influenza from swine to humans who work with swine was documented in a small surveillance study performed in 2004 at the University of Iowa.[18] This study among others forms the basis of a recommendation that people whose jobs involve handling poultry and swine be the focus of increased public health surveillance.[17] The 2009 swine flu outbreak is an apparent reassortment of several strains of influenza A virus subtype H1N1, including a strain endemic in humans and two strains endemic in pigs, as well as an avian influenza.[19]
The CDC reports that the symptoms and transmission of the swine flu from human to human is much like seasonal flu, commonly fever, lethargy, lack of appetite and coughing. Some people with swine flu also have reported runny nose, sore throat, nausea, vomiting and diarrhea.[20] It is believed to be spread between humans through coughing or sneezing of infected people and touching something with the virus on it and then touching their own nose or mouth.[21] Swine flu cannot be spread by pork products, since the virus is not transmitted through food.[21] The swine flu in humans is most contagious during the first five days of the illness although some people, most commonly children, can remain contagious for up to ten days. Diagnosis can be made by sending a specimen, collected during the first five days, to the CDC for analysis.[22]
The swine flu is susceptible to four drugs licensed in the United States, amantadine, rimantadine, oseltamivir and zanamivir, however, for the 2009 outbreak it is recommended it be treated with oseltamivir and zanamivir.[23] The vaccine for the human seasonal H1N1 flu does not protect against the swine H1N1 flu, even if the virus strains are the same specific variety, as they are antigenically very different.[24]
