Abstract: A nucleic acid comprising a 13 base sequence selected from the group consisting of tcGg TtccgCt Gc, tcGgTtccgCc Ac, tcGgTcCcaTcCc, tcGgTtCcaTcCc, ttGgTcCcaTcCc, ttGgTtCcaTcCc, tcGgTcccgTcCc, and tcGgTtccgTcCc, where A and a are adenine, C and c are cytosine, G and g are guanine, and T and t are thymine or uracil, and complementary sequences thereof; provided that only a very limited number of additional bases are included at the 5? and 3? ends of the sequences. The use of these nucleic acids for differentiating picornaviruses, and bioassay methods employing these nucleic acids in nucleic acid amplification assays, are also disclosed.