Swine influenza, Avian influenza and Human flu

Friday, June 12, 2009

From Wikipedia, the free encyclopedia

Swine influenza (also called swine flu, hog flu, and pig flu) is an infection of a host animal by any one of several specific types of microscopic organisms called "swine influenza virus". A swine influenza virus (SIV) is any strain of the influenza family of viruses that is usually hosted by (is endemic in) pigs.[2] As of 2009, the known SIV strains are the influenza C virus and the subtypes of the influenza A virus known as H1N1, H1N2, H3N1, H3N2, and H2N3. Swine influenza is common in pigs in the midwestern United States (and occasionally in other states), Mexico, Canada, South America, Europe (including the United Kingdom, Sweden, and Italy), Kenya, Mainland China, Taiwan, Japan and other parts of eastern Asia.[2]
Transmission of swine influenza virus from pigs to humans is not common and does not always cause human influenza, often only resulting in the production of antibodies in the blood. The meat of the animal poses no risk of transmitting the virus when properly cooked. If transmission does cause human influenza, it is called zoonotic swine flu. People who work with pigs, especially people with intense exposures, are at increased risk of catching swine flu. In the mid-20th century, identification of influenza subtypes became possible, this allows accurate diagnosis of transmission to humans. Since then, fifty confirmed transmissions have been recorded, Rarely, these strains of swine flu can pass from human to human. In humans, the symptoms of swine flu are similar to those of influenza and of influenza-like illness in general, namely chills, fever, sore throat, muscle pains, severe headache, coughing, weakness and general discomfort.
The 2009 swine flu outbreak in humans is due to a new strain of influenza A virus subtype H1N1 that contains genes closely related to swine influenza.[3] The origin of this new strain is unknown. However, the World Organization for Animal Health (OIE) reports that this strain has not been isolated in pigs.[4] This strain can be transmitted from human to human,[5] and causes the normal symptoms of influenza.[6]
Pigs can become infected with human influenza, and this appears to have happened during the 1918 flu pandemic[citation needed] and the 2009 swine flu outbreak.[citation needed]

Bird flu may refer to:
Biology and disease
Avian influenza, influenza endemic to birds.
Influenzavirus A, the causative agent for bird flu; the genus of the Orthomyxoviridae family. of viruses to which all viruses responsible for Avian influenza belongs to, but also includes viruses that are endemic to humans and other animals.
H5N1, a subtype of Influenza A virus endemic to birds, currently perceived as a significant emerging pandemic threat.

Avian influenza, sometimes Avian flu, and commonly Bird flu, refers to "influenza caused by viruses adapted to birds."[1][2][3][4][5][6][7] Of greatest concern is highly pathogenic avian influenza (HPAI).
"Bird flu" is a phrase similar to "Swine flu," "Dog flu," "Horse flu," or "Human flu" in that it refers to an illness caused by any of many different strains of influenza viruses that have adapted to a specific host. All known viruses that cause influenza in birds belong to the species: Influenza A virus. All subtypes (but not all strains of all subtypes) of Influenza A virus are adapted to birds, which is why for many purposes avian flu virus is the Influenza A virus (note that the "A" does not stand for "avian").
Adaptation is non-exclusive. Being adapted towards a particular species does not preclude adaptations, or partial adaptations, towards infecting different species. In this way strains of influenza viruses are adapted to multiple species, though may be preferential towards a particular host. For example, viruses responsible for influenza pandemics are adapted to both humans and birds. Recent influenza research into the genes of the Spanish Flu virus shows it to have genes adapted to both birds and humans; with more of its genes from birds than less deadly later pandemic strains.

Human flu is a term used to refer to influenza cases caused by Orthomyxoviridae that are endemic to human populations (as opposed to infection relying upon zoonosis). It is an arbitrary categorization scheme, and is not associated with phylogenetics-based taxonomy. Human flu-causing viruses can belong to any of three major influenza-causing Orthomyxoviruses — Influenza A virus, Influenza B virus and Influenza C virus.
The annually updated trivalent influenza vaccine contains two hemagglutinin (HA) surface glycoprotein components from Influenza A virus strains and one from B influenza.
Most human flu is a non-pandemic flu that is slightly different from the main human flus that existed in last year's flu season period. This type of flu is also called "common flu" or "seasonal flu" or "annual flu". It causes yearly flu epidemics that are generally not deadly except to the very old or very young.