RT-PCR/electrospray ionization mass spectrometry (ESI-MS) assays were developed recently to enable the potential detection and typing of microbial agents, including influenza [9] [10] [11] [12] [13] [14] , during the same flow procedure [15] [16] [17] . This technology relies on the analysis of nucleotide base *Address correspondence to this author at the Laboratory of Virology, Division of Infectious Diseases, University of Geneva Hospitals, 4 Rue Gabrielle-Perret-Gentil, 1211 Geneva 14, Switzerland; Tel: ++41 22 3724079; Fax: ++41 22 3724097; E-mail: samuel.cordey@hcuge.ch composition signatures of highly variable selected regions based on the measurement of the molecular weight of PCR amplicons [12, 18] .