The goal of this study is to compare the efficacy of the surgical mask to the N95 respirator in protecting nurses from influenza in the hospital setting. The investigators propose a non-inferiority randomized controlled trial whereby nurses are randomized to either a surgical mask or an N95 respirator when caring for patients with febrile respiratory illness during the influenza season. The hypothesis is that the surgical mask offers similar protection against influenza to that of the N95. The specific objective of the study is to assess whether the rates of influenza (laboratory-confirmed by PCR and HAI assay), as well as secondary outcomes (influenza-like illness, work-related absenteeism, physician visits for respiratory illness, and lower respiratory infection), are similar among nurses using a surgical mask compared to those using an N95 respirator.