Life-threatening Respiratory Failure from H1N1 Influenza: Lessons from the Southern Cone Outbreak

A sharp increase in the hospitalization rate for pneumonia, particularly among adults between 20 and 40 years old, and an unusual series of deaths, coincident with an increase in laboratory-confirmed influenza cases, were reported in the spring of 2009 in Mexico. This outbreak appeared after the end of influenza season, and was associated with mortality in a younger age-group than the pattern observed in temperate areas in the northern hemisphere [1]. The concurrent finding of a novel, swine-origin influenza A virus (so called pandemic influenza [H1N1] 2009) from infected children in the United States [2] completed the picture.