Full-length poliovirus genomic RNA was transcribed from MluI-linearized plasmid prib(+)XpA using T7 RNA polymerase as previously described [36] . Poliovirus RNA was mixed with HeLa total RNA in a dilution series ranging from 10 22 to 10 26 poliovirus gRNA per HeLa RNA. Randomly-primed dsDNA libraries were prepared, hybridized to the Virochip, and analyzed as described above.