Types of Swine Influenza
Key Facts About Swine Influenza and Its Classification
Swine influenza (also called swine flu, or pig flu) is an acute respiratory infection diseases originated by the strains of influenza viruses that regularly cause outbreaks in pigs. Swine influenza types do not normally infect human population if consumed as meat but chiefly influence when exposed to affected pigs directly. Mainly characterized by the symptoms of high fever, lethargy, nasal discharge, cough, severe headache, weight loss and dyspnea the transmission of influenza in humans is also called as Zoonotic swine flu.
Influenza Viruses Changing All the Time
- Even though the Avian, human and Swine influenza types of viruses belong to the same class called Orthomyxo viruses, due to distinct gene segments the re-assortment of two different strains take place leading to a new type of virus. These re-assortments or mixing may change the virus characteristics and generally occurs when two different species infect the same host.
- Swine influenza types do not normally affect human beings but sporadic human infections with swine influenza viruses have been noticed in many countries especially in United States. Hence, when an influenza virus that usually appears in swine is discovered in a person, it is called a “variant influenza virus.” This type of virus is normally denoted by the letter “v” to the end of each virus subtypes as H1N1v, H3N2v and H1N2v.
Classification of Influenza Viruses
- One of the most important outbreaks throughout the world in the mid 20th century is the identification of swine influenza subtypes and its transmission to human population. Like human influenza viruses, over the years the swine influenza viruses also have gone through many transformations and variations. Among the three genera of influenza types A, B and C, the strains that are widely found in pigs are swine influenza types A and C.
- Swine influenza is mainly categorized into various subtypes based on the two viral surface antigens known as Hemagglutinin (H) and Neuraminidase (N). By the end of 2009, the swine influenza types that have been isolated in pigs are identified as influenza C and the subtypes of influenza A known as H1N1, H1N2, H3N1, H3N2, and H2N3. However, recent study shows that the H1N1 and H3N2 are the most common basis for the possible epidemic in various countries.