It was in March 2009 that we began to hear about swine flu, also known as influenza A, or H1N1 flu. The first cases were detected in Mexico. Since then, people infected with this virus have been identified in most countries of the world, the WHO today speaking of a pandemic. This is the first time that this virus is transmitted in humans.
Why do we also speak of "swine flu" about influenza A? Because the origin of the infectious agent - the virus - comes from pigs. Swine flu is an acute respiratory disease of the pig, caused by one or more influenza A viruses. Swine flu viruses are most often of the H1N1 subtype, but other subtypes can be identified (by example H1N2, H3N1, H3N2).
When pigs are contaminated with different types of influenza viruses (human, avian, swine), this promotes the appearance of a new hybrid influenza virus that can infect humans. In recent years, human cases had already been detected in Europe (well before 2009). But this is the first time that this A / H1N1 virus is transmitted in humans and causes such an inter-human contamination.
The causes of contamination are well known. In most cases, swine flu is not dangerous for humans, except when a new type of virus appears that can infect humans and cause more or less serious symptoms.
The transmission of this A / H1N1 virus can be carried out:
> From one pig to another.
> From pork to man: mainly by air. Eating pork does not present any risk because cooking destroys viruses.
> From man to man: the transmission is done by contact with secretions containing viral particles (cough, postilions, by hand-carrying ...). Transmission routes are respiratory and contagion is spread by inhalation of the virus, especially in enclosed areas, or when people are in close contact. Today is the main mode of transmission of this virus that is quite contagious.
In March 2009, influenza A cases were identified in America (mostly in Mexico). Then cases gradually became known all over the world. Due to the pandemic, in June 2009, WHO raised its alert level to the maximum level (6). And in September 2009, the number of people affected by influenza A was higher than that affected by seasonal flu.