K-4206. Assessing the Quantitative Efficiency of Surgical Masks (SM) vs N95 Masks (N95-M) in Filtering Respiratory Secretions Among Patients with Acute Influenza A and B
Session: Slide Session: Seasonal and Pandemic Influenza
Tuesday, October 28, 2008: 12:00 AM
Room: Room 150B
Background: Influenza virus is a major cause of morbidity and mortality spread via respiratory secretions created during coughing or sneezing. Although CDC Guidelines recommend Influenza infected patients and healthcare workers wear masks to reduce transmission, there is minimal in vivo evidence to assess their efficacy. Methods: Acutely ill patients with a presumptive diagnosis of influenza were recruited from our hospital’s emergency department, during the 2007 winter. Consenting patients had influenza assessed by Binax NOW® Influenza A and B point-of-care test, followed by a nasal swab for RT-PCR for respiratory viruses. Binax-positive patients participated in a standard protocol to assess mask efficacy. Patients sequentially coughed onto a 10cm petri dish containing 1ml viral transport medium (VTM) wearing each of the following: no mask, N95-M, SM, no mask. The filtration efficiency of each mask compared to no-mask controls was assessed by quantitative RT-PCR on each VTM sample. Results: Of the 26 patients enrolled, 10 were Binax-positive and 9 were well enough to complete the protocol - all 9 were VTM PCR-positive with no mask. Both SM and N95-M had identical filtration efficiency with 9/9 having no influenza detected on RT PCR. Among the 19/26 patients who had influenza confirmed by nasal swab PCR (A, n=15; B, n=4) the Binax-NOW demonstrated sensitivity/specificity of 53%/100% and 50%/100%, respectively. Conclusions: This study is the first to assess the relative efficiency of SM vs N95-M in vivo among acutely unwell patients with influenza - both masks appeared to be highly effective in filtering Influenza during coughing.. These preliminary findings suggest the use of either SM or N95-M on acutely ill influenza patients is likely to reduce transmission.
Chris Birch, Victorian Infectious Diseases Reference Laboratory, Douglas Johnson, Austin Hospital, Melbourne, Australia, Julian Druce, Victorian Infectious Diseases Referance Laboratory, Michael Grayson, Austin Hospital and  D. F. Johnson, None.