First-round PCR products (2 µl) are transferred to 48 µl of second PCR reaction mixture, containing 5 µl of 10X PCR buffer, 25 pmol each primers aBT1, aCT2, aET3, aDT4, aAT8, aFT9 and RVG9, 0.2 mM each dATP, dGTP, dCTP and dTTP, 2mM MgCl2, 2.5 U of Taq polymerase. Second-round cycling conditions are identical to first round, except that only 25 cycles are run. The PCR products are analyzed by gel electrophoresis to identify expected lengths of amplified VP7, allowing determination of genotype. Other primer sets, PCR conditions and/or sequencing is used to distinguish genotype when/if the initial primers fail.