Identification of 19 novel Hepatitis C virus subtypes - further expanding HCV classification by Hedskog, C, Parhy, B, Chang, S, Zeuzem, S, Moreno, C, Shafran, SD, Borgia, SM, Asselah, T, Alric, L, Abergel, A, Chen, J-J, Collier, J, Kapoor, D, Hyland, RH, Simmonds, P, Mo, H, Svarovskaia, ES