Almost 70% of HCV patients were co-infected with HIV, which is similar to the percentages reported in other countries . In 60 of the 88 patients who were positive only for anti-HCV, and in 18 of the 25 patients who were positive for HBsAg and anti-HCV (Table 2), HCV RNA was detected and sequenced in the core/E1 region (Tables 1 and 2). Phylogenetically, the 78 strains belonged to HCV subtypes 1b (53.8%), 3a (38.5%), 1a (5.1%), 4a (1.3%) and 4d (1.3%) (Table 2; Fig. 2). A previous study in 1997  reported that subtype 1b was the most prevalent subtype (76%), followed by subtype 3a (19%) and single cases of subtypes 1a and 2a, which suggests that the prevalence of subtype 3a has increased and that fewer subtype 1b strains are now circulating. Subtypes 1b and 3a are also dominant over other subtypes in Russia, Estonia and western Europe . While both subtypes have a similar prevalence (45%) in Russia, the relative prevalence of subtype 1b over subtype 3a is three-fold greater in Estonia (71% vs. 24%; ) and 6.5-fold higher in western Europe (58% vs. 9%). In Russia and Estonia, the prevalence of all other subtypes is <2% and <1%, respectively, while subtype 1a accounts for 20% of strains in Europe. Thus, with a 1.5-fold dominance of subtype 1b over subtype 3a, and a prevalence of 5.1%, the subtype pattern of HCV in Belarus is similar to that in Russia, although not without a clear western European influence. Subtypes 1a, 4a and 4d were found only in HIV-positive patients, while the prevalences of subtypes 1b and 3a were 70.4% and 29.6%, respectively, in HIV-negative patients, and 45.1% and 43.1%, respectively, in HIV-positive patients (Table 2). Similar studies, e.g., in Spain , have also revealed that subtypes 1a and 3a are more prevalent among HIV-positive donors, indicating that separate transmission networks exist for different HCV subtypes, e.g., among intravenous drug users .
In the HCV strains found in Belarus, the average distances at the nucleotide level were 5.7–7.1% within subtypes, and 22.4–33.8% among subtypes, with an average distance among all Belorussian strains of 21.8%. The diversity within subtype 3a in Belarus was 1.7-fold less than the diversity of all worldwide strains belonging to the same subtype, while for subtype 1b it was 1.2-fold less. Despite the higher prevalence of subtype 1b, this may indicate that subtype 3a has been circulating longer in Belarus, or that it has been introduced on multiple occasions from various sources and/or countries. BLAST searches of the different HCV strains did not reveal a closer relationship of Belorussian subtypes with other strains from the same geographical region, but indicated similarities for both subtypes 1b and 3a with strains found worldwide. For subtype 1b, this could be explained by the worldwide use of contaminated blood products, e.g., in anti-D immunoglobulin in 1977 . However, for subtype 3a, circumstances similar to those in Egypt may have caused its spread . At the protein level, the HCV strains did not reveal any amino-acid substitutions that were specific to strains or subtypes found in Belarus, thereby confirming that multiple introductions from abroad had probably occurred.
In conclusion, HBV genotype D strains in Belarus form phylogenetic clusters (D1–D4) that are compatible with the four subtypes proposed recently, although the inter-subtypic distances may be lower than required. The relative prevalence of genotypes of both HBV and HCV in Belarus reflect the frequencies found in Russia, although with clear European influences, possibly explained by the socio-political context of the country. Surprisingly, the virus variants do not seem to be related to those from neighbouring countries.