Why Swine Flu Spread In People

Influenza A (H1N1) virus is a subtype of influenza A virus and was the most common cause of human influenza (flu).

Swine influenza (also called swine flu, hog flu, or pig flu) is an infection by any one of several types of swine influenza virus. Swine influenza virus (SIV) is any strain of the influenza family of viruses that is endemic in pigs. As of 2009, the known SIV strains include influenza C and the subtypes of influenza A known as H1N1, H1N2, H3N1, H3N2, and H2N3.

Swine influenza virus is common throughout pig populations worldwide. Transmission of the virus from pigs to humans is not common and does not always lead to human influenza, often resulting only in the production of antibodies in the blood. If transmission does cause human influenza, it is called zoonotic swine flu. People with regular exposure to pigs are at increased risk of swine flu infection. The meat of an infected animal poses no risk of infection when properly cooked.

The H1N1 swine flu virus was first identified in people in April 2009 but genetic research later suggested it had in fact been circulating for at least a decade and probably longer in pigs.

The H1N1 swine flu virus underwent a mutation and used a new trick to spread efficiently in people.Typically, a flu virus needs two amino acids -- lysine and asparagines -- on specific sites on its structure before it can jump from animals to people and multiply efficiently in human cells.

But the H1N1 remained a puzzle for scientists because they could not find the amino acids in those two locations.

In an experiment with mice, by scientists discovered the lysine amino acid was residing instead in a completely different position, but it allowed the virus to be just as effective in adapting to human cells.

This is definitely a breakthrough, to help predict the possibility of future flu pandemics.

Source : REUTERS