Total RNA was extracted from hMPV-infected cells using TRizol (Invitrogen) reagent according to the manufacturer's instructions followed by phenol/chloroform (Amresco) extraction and ethanol precipitation. RT-PCR products of total hMPV RNAs were generated using a one step Ultrasense RT-PCR kit (Invitrogen) with sense and anti-sense primers designed to generate 1 to 2 kb fragments from total RNA. Genomic RNA was amplified with a two-step Super Script III platinum RT-PCR kit (Invitrogen). To ensure that only genomic RNA was amplified in the two-step process, only the sense primer was present during the RT step, the RT was deactivated by treatment of the product at 94°C for 15 minutes, and phenol/chloroform extraction was performed on the RT product to remove any residual RT enzyme prior to the PCR reaction. Sequence analysis was performed only on DNA fragments of the expected size isolated from agarose gels using a gel extraction kit (Qiagen).