During April 2009, a novel swine-origin influenza A (H1N1) virus (S-OIV) was identified in California and in Mexico as the cause of human respiratory disease, originating a pandemic [3, 4] . As of February 2010, 700 000 laboratory-confirmed cases of novel H1N1 influenza virus and 14 000 deaths have been reported globally. Most affected patients present with influenza-like symptoms and have a benign course [5] . However, patients with comorbidities as cancer and chronic diseases may show a serious clinical presentation, characterized by respiratory failure with variable severity [6, 7] .