[One hundred years after the "Spanish" flu].

The "Spanish" flu pandemic, which occurred a century ago, is considered the most devastating in human history. An estimated one third of world population fell ill with flu and more than 2.5% of them died. The course of the epidemic had two main waves (1918 and 1919) and showed an unusual W-shaped morbidity/mortality distribution. Death was not a direct outcome of flu itself but rather a consequence of secondary bacterial bronchopneumonia, for which antibiotics had not yet been discovered. Pre-existing pulmonary tuberculosis was also accountable for increased flu death rates during the pandemic. As it happened in Europe, in Argentina the epidemic had two main waves, with ample variation in mortality by region. Available treatment at the time included diet, throat antiseptic rinses, low doses of quinine valerianate, salicylates, codeine as a cough suppressant, and camphor oil. Primitive anti-pneumococcal vaccines and immune sera were also applied. Upon the disclosure of the whole RNA sequence of the 1918 influenza virus genome, by means of reverse genetics it was possible to assemble viral particles resembling those of the deadly pandemic. The reconstituted virus proved to be extraordinarily virulent for mice. Current seasonal flu vaccines help to reduce, but not to abolish, the risk of another pandemic. The ongoing development of "universal" vaccines against influenza conferring reliable and long-lasting immunity may prevent its global spread in the future.