Shift in predominating subtype of HCV from 1b to 3a in St. Petersburg mediated by increase in injecting drug use

The genotypes of 149 HCV strains from St. Petersburg were determined by lim ited sequencing and phylogenetic analysis within the NS5B region. One hundr ed two strains derived from patients that attended infectious disease clini cs, of whom 48 admitted injecting drug use, and 47 derived from dialysis pa tients. Subtype 3a was predominant in the patients from infectious disease clinics, both in patients that admitted injecting drug use (56%) and in tho se with unknown source of infection (46%). However, 89% of the strains from dialysis patients belonged to subtype 1b. Eleven of twelve characterised s trains from recent cases of hepatitis C at these units were at phylogenetic analysis shown to be related to strains already circulating there, demonst rating that within the dialysis units nosocomial transmission is the most i mportant route of HCV infection. The predominance of subtype lb strains in dialysis patients indicates that these strains have been circulating for a long time in dialysis units. The predominance of subtype 3a also among pati ents who did not admit drug use and that their strains were intermixed with the strains from injecting drug users in the phylogenetic analysis shows t hat the increase in injecting drug use is the major factor that explains th e recent spread of HCV in the St. Petersburg population. This supports the concept that injecting drug use remains the major route for HCV infection i n developed countries and that the control of drug abuse is the most import ant measure to prevent its spread. (C) 2001 Wiley-Liss, Inc.