H1N1: A Subtype of Influenza a Virus

Swine flu and human influenza are one and the same and that pigs had gotten the disease from humans. Influenza viruses,members of the Orthomyxoviridae family have three (3) types of flu virus, types A, B, And C. Influenza A viruses are divided into two (2) viral surface glycoproteins: the hemagglutinin (H) and the neuraminidase (N) antigens. Type A includes three (3) subtypes: H1N1, H2N2, H3N2. The current subtypes of influenza A viruses circulating widely among humans are A (H1N1) and A (H3N2). Influenza A viruses circulate primarily on aquatic birds and also on other animals like pigs, horses, seals and others. Type A viruses with an H or H/N combination are known to cause global epidemics or pandemics with highest incidence in "winter" season. Due to the natural inclination of its antigens to undergo variation, influenza A virus exhibits the most extensive and sever outbreaks. These variations are referred to as "antigenic shifts" on viral strains,which results in the expression of a different H and/or N antigens. In human infections, three (3) major H antigens (H1,H2 and H3) and two (2) N antigens (N1 and N2) are recognized.

Influenza B virus circulate among humans and their outbreak are less extensive and less severe. it is due to the fact that their H and N antigens undergo a lesser frequency of variation. This also means that they are not usually associated with epidemics. it is estimated that 25% in school outbreaks are due to influenza A (H1N1) and influenza B. Influenza C virus usually exhibits sporadic cases and minor localized outbreaks. So, they are considered less of a disease burden than influenza A and B because the virus is infrequently associated with human disease. Influenza A and B viruses are included in seasonal influenza vaccines.

Similar flu symptoms. Influenza is an acute and a highly contagious infection of the respiratory tract. We have to note that if there is presence of infection there is also fever. Hallmarks of influenza to man are high fever, muscle aches and pains (myalgia) and drippy noses. On the other hand pigs got runny noses, fevers and watery eyes like that of human symptoms. Influenza spreads through "airborne" inhalation (droplet infection) of mouth and nose on both pigs and man. The virus can also enter another body through direct and indirect contact. This is the main reason why handwashing is highly recommended when we go to public places.

For more info. visit these websites:

www.who.int.flunet

www.who.int./csr/disease/influenza/centres/en/index.html.

www.who.int/csr/disease/influenza/en/

www.who.int/influenza