Severe pandemic (H1N1) 2009 influenza with false negative direct fluorescent antibody assay: Case series

Between May and June of 2009 we observed 4 patients that presented with severe influenza-like symptoms and respiratory failure. All cases tested negative for influenza A and B by direct fluorescent antibody assay. Further investigation revealed all cases to be positive for pandemic (H1N1) 2009 influenza virus by real-time RT-PCR This article includes a description of these cases and the characteristics associated with them. (C) 2009 Elsevier B.V. All rights reserved.