In 2011, a study was made in order to establish the origin of swine flu and of swine flu symptoms, which are incredibly similar to those of regular flu, but unfortunately, much more dangerous. Apparently, swine flu was traced even before 1918. Even if the pandemics appeared and made a lot of victims in 2009, its phylogenetic origin is very old. In the beginning of the 20th century, the virus, with avian background, crossed the boundaries between species and infected humans for the first time. H1N1 appeared then and infected people in America, but also pigs, thus the popular name of this influenza, better known as swine flu. Until 1957, the virus was continuously transmitted. It even developed at some point in a new virus named H2N2. Since it transformed in H2N2, the original H1N1 was never encountered until 1976. At some point, the two different viruses met, thus resulting a new one, H3N2. Until present, H3N2 was a simple and regular flu and did not provoke any sort of problems to people or to other species.

In the mid 1970s, the flu evolved once again and H1N1 reemerged as a seasonal strain of flu. At some point, H2N2 was believed to be extinct. At the end of the 1970s, H1N1 infected pigs and developed into a swine virus which still exists in present. The most important part of the transmission of the whine flu was between 1990 and 1993. This period influenced the serious outbreak from 2009. At some point in the 1990s, North American pigs contracted the swine virus, humans contracted H3N2 virus and after these, the H1N2 swine strain was generated. In 2009, H1N2 infected humans in the same time as H1N1 swine strain, developing a new strain of H1N1 which caused the horrible pandemic that affected the whole world.

In June 2009, the whole world understood the gravity of the situations when the World Health Organization raised the pandemic alert at phase 6, the highest level. The swine flu and the swine flu symptoms were spread globally and there were cases of sick people in most of the countries. Even if the disease was not so severe, the fact that it was spread all around the world worsened the situation. Because the human to human transmission rate is high, it was very easy for such a pandemic to appear.