Swine influenza (swine flu) is a respiratory disease caused by type A influenza (IAV) viruses that regularly cause outbreaks of influenza in pigs.
Swine influenza viruses may circulate among swine throughout the year, but most outbreaks occur during the late fall and winter months, similar to outbreaks of seasonal influenza in humans.
When an influenza virus that normally circulates in swine (but not people) is detected in a person, it is called a “variant influenza virus.” Swine flu viruses do not normally infect humans, however, sporadic human infections with influenza viruses that normally infect swine have occurred.
It is possible for the genes of swine, human, and avian influenza viruses to mix and create a new virus. This type of major change is known as antigenic shift. If this new virus causes illness in people and can be transmitted easily from person-to-person, an influenza pandemic can occur. This is what happened in 2009 when an influenza A H1N1 virus with swine, avian and human genes emerged in the spring of 2009 and caused the first pandemic in more than 40 years.
The following infographic explains how antigenic shifts can occur:
https://en.wikipedia.org/wiki/Antigenic_shift
What is H1N1 Swine Flu?
H1N1 Swine Flu In Humans
The new H1N1 strain was called swine-origin influenza virus A (S-OIV) (3).
It was first detected in people in the U.S. in 2009 and soon after elevated to a global pandemic (1).
The pandemic H1N1 was a new virus when it emerged and most people had no or little immunity to it (11).
The H1N1 virus that caused that pandemic is now a regular human flu virus and continues to circulate seasonally worldwide (1).
Continue browsing the pages above to learn more about H1N1 Swine Flu.