IFITM3 and influenza: In addition, the hospitalization criteria that were used in the different health units might not be uniform and could be different from influenza A(H1N1)pdm09 positive and negative cases given the pandemic alert and the indications of the health authorities This differential criterion for hospitalization could explain the presence of the IFITM3 rs12252 association in the negative influenza patients and the absence in the positive influenza patients.