How did the swine flu become an epidemic infection?

On 11 June, 2009 the Word Health Organization declared the A/H1N1 influenza epidemic to be a worldwide pandemic (level 5, later as level 6). It was an appropriate call. It was not the pandemic we had been dreading ever since the A/H5N1 had first appeared in Hong Kong 1997, had been stamped out, and then appeared again in 2003. read more

This is an influenza virus that had never been identified as a cause of infections in people before the current H1N1 pandemic. Genetic analyses of this virus have shown that it originated from animal influenza viruses and is unrelated to the human seasonal H1N1 viruses that have been in general circulation among people since 1977. read more

Swine influenza is an infection caused by any one of several types of swine influenza viruses. Swine influenza virus or swine-origin influenza virus 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, H2N1, H3N1, H3N2, and H2N3. The Swine flu was initially seen in humans in Mexico in 2009, where the strain of the particular virus was a mixture from 3 types of strains. read more