One hundred years ago, it took place the most important epidemic crisis of 20^th Century, until the AIDS appearance, classified as the genetic mother of all the influenza’s pandemics (Taubenberger, Jeffery K.; Morens, David M. “1918 Influenza: the mother of all pandemics”, Emerging Infectious Diseases, 2006, 12(1):15-22). This serious sanitary crisis, responsible for a huge number of deaths currently estimated in 50 – 100 millions, has gone down in history as “Spanish Influenza”.

 

However, this term, coined by European press, does not reflect the true origin of this pandemic but was the result of the circumstances surrounding it. Its coincidence with the end of the First World War and the existing military censorship in the countries that participated in that war. This facilitated that it was silenced when it appeared in them two months before the beginning of the epidemic in Madrid, coinciding with the days before the San Isidro festivities on May 15^th.

 

Despite the century that has passed and the studies that has been made for trying to figure out the secrets of this serious sanitary crisis, which infected more than a third of the world population and had a lethality rate higher than 2,5%, extremely over to 0,1% rate of other influenza pandemics, it stills a mystery the reached scale and the larger mortality caused in young-adult population. This traumatic experience produced a great social shock and a fear of the repetition of another disaster with similar dimensions. This new risk perception of influenza has lasted during the last century and has determined the social reactions of new influenza pandemics produced in 20^th Century (1957-1958 and 1968-1969) and the 21^st Century (2009-2010); and also it has been implemented WHO programmes to combat this disease, including, among other things, annual vaccination against influenza as a means of preventing it.