The World Health Organization (WHO) has announced that the H1N1 influenza pandemic has largely run its course and is now over.

Margaret Chan, director-general of WHO, says the world is now moving into the post-pandemic period, meaning “based on experience with past pandemics, we expect the H1N1 virus to take on the behavior of a seasonal influenza virus and continue to circulate for years to come.”

Called many names since its discovery in the spring of 2009, the World Organization for Animal Health (OIE) recommends the virus be referred to as “North American influenza,” in keeping with the naming of other outbreaks of influenza in the human population.

The Centers for Disease Control (CDC) has determined that the 2009 H1N1 flu virus contains genetic pieces from four different virus sources, which is unusual. The virus consists of North American swine influenza viruses, North American avian influenza viruses, human influenza viruses and swine influenza viruses found in both Asia and Europe.

The 2009 H1N1 flu virus was first reported in late March/early April 2009 in central Mexico and the border states of California and Texas. Since that time, it has become a worldwide pandemic.

To date, most animals infected with H1N1 became infected after their owners had become ill with flu-like symptoms and have shown mild respiratory illness or no illness at all. In most cases, animals have fully recovered.