Swine flu started among birds transferring diseases. The diseases mutated from Avian Flu to Swine flu and became common in pigs.
In 2009, a new strain of swine flew had developed the ability to exist among humans. The first case of swine flu among humans was in Mexico. This strain became known as the H1N1 virus.
H1N1 quickly became a pandemic in 2009. The virus spread through Mexico and across the world with rapid speed. It passed like any other flu, through the air and human contact. The disease cases were reported across the globe, but survival rate was much smaller in underdeveloped countries.
As Swine Flu spread throughout the United States, some areas were highly affected. This video shows where the disease was more prevalent.