Viral RNA from the diagnostic swabs or RNA extracted from MDCK cell cultures was extracted using the DNA minikit (Qiagen, Inc, Valencia, CA, USA) according to manufacturer's instructions. RNA was reverse-transcribed to cDNA using customized random primers designed using LOMA (11) and then amplified by PCR using proprietary H1N1(2009) specific primers. The presence of H1N1(2009) in the samples was confirmed using a separate real-time PCR assay based on the published primer sequences from the Centre for Disease Control and Prevention (CDC), USA.