Objectives. To investigate the proportion of different genotypes in countryside microregions in southern Brazil, and their association with risk factors. Methods. Cross-sectional study including a convenience sample of patients who tested positive for HCV-RNA and were referred to a regional health center for genotyping, from December 2003 to January 2008. Data were obtained through the National Disease Surveillance Data System, from laboratory registers and from patient charts. Identification of genotypes was carried out using the Restriction Fragment Length Polymorphism “in house” technique. Independent associations with genotypes were evaluated in multinomial logistic regression and prevalence rates of genotypes were estimated with modified Poisson regression. Results. The sample consisted of 441 individuals, 41.1±12.0 years old, 56.5% men. Genotype 1 was observed in 41.5% (95% CI 37.9–48.1) of patients, genotype 2 in 19.3% (95% CI 15.0–23.6), and genotype 3 in 39.2% (95% CI 35.6–43.0). HCV genotype was significantly associated with gender and age. Dental procedures were associated with higher proportion of genotype 2 independently of age, education, and patient treatment center. Conclusions. The hepatitis C virus genotype 1 was the most frequent. Genotype 2 was associated with female gender, age, and dental procedure exposition.
1. Background
Hepatitis C virus (HCV) was identified in 1989 and has been considered a major cause of chronic liver disease worldwide [1]. There is a great variability in its geographical distribution, associated to the degree of nation development. High prevalence is found in Africa and Asia, in opposite to low-prevalence areas localized in industrialized nations in North America, north and west Europe, and Australia [2–4]. In Brazil, according to the World Health Organization, the estimated prevalence ranges from 2.5 to 4.9% [5].
Transmission of HCV has been mainly related to intravenous drug use since blood products transmission has decreased in most developed countries. On the other hand, contaminated injection equipment appears to be the major risk factor for HCV infection in several countries and sharing personal hygiene objects might explain the transmission of virus C to those not infected by the usual routes [6]. The distribution of different genotypes also varies according to the studied population and viral transmission risk factors. In studies from Spain there is a predominance of genotypes 1a and 1b [7, 8] while in other European regions genotype 2 is usually the most prevalent [4, 9–11]. Genotype 1 predominates in Central America [12], and in Latin-American countries such as Argentina [13, 14] and Venezuela [15] genotypes 1 and 2 account for 90% of cases. In Brazil, genotypes 1 and 3 are the most frequent [16, 17], but in Da Silva et al. study [18] almost half of the hepatitis C patients from South of Brazil were infected by genotypes 2 and 3. In this study we investigated the proportion of different genotypes in countryside microregions of a state in southern Brazil, and their association with sociodemographic characteristics and HCV infection risk factors.
2. Methods
A cross-sectional study included a nonprobabilistic sample of patients under followup at the HCV program of Brazilian Public Health System, in countryside cities of southern Brazil. Patients from the Brazilian Public Health System, who tested positive for anti-HCV, were referred for genotyping, from December 2003 to January 2008, to a main regional health center in the southernmost state of Brazil. Genotyping was routinely performed to choose the recommended treatment according HCV genotype. HCV-RNA was carried out as a confirmatory test and the samples of all patients genotyped at the central laboratory in the period were included consecutively.
Retrospective data collection was carried out and included demographic and socioeconomic characteristics, exposure and behavioral risks factors. Data were obtained through the National Disease Surveillance Data System (SINAN), laboratory registers and from patient charts at their cities of origin. Researchers were trained before data collection start, and quality control was performed by random repetition of data collection in 10% of the sample.
Identification of genotypes was carried out using the Restriction Fragment Length Polymorphism “in house” technique [19], which uses universal primers and real time-polymerase chain reaction to amplify specific genomic sequences and it compares to strip hybridization. Next, DNA fragments of different sizes are generated by enzymatic restriction digestion, which recognizes specific cleavage sites for each genotype. This method allows differentiation of genotypes 1, 2, 3, 4, 5, and 6 [20]. Preanalytic quality control included the sample and the reagents preparation, amplification and detection, and environment control.
The study has been performed according to the World Medical Association Declaration of Helsinki and approved by the Ethics Committee of Passo Fundo University, Brazil. Regional health centers consented with the study, and an agreement on data use was signed.
A sample size of 384 individuals was necessary to estimate a genotype 1 prevalence of 50%, with a 95% confidence interval and a 10% prevalence variation. Considering the less expected genotype 2, 292 patients would be necessary to determine 5% ±5 prevalence.
Data was described using frequency and central tendency measures, and 95% confidence intervals were calculated when applicable. Associations between risk factors and genotype were analyzed using chi-square. To identify independent associations with genotype we used multinomial logistic regression. Models were tested taking into account variables with a P value < 0.20 on the crude analysis, and those that remained independently associated with the genotype were included in the final model. To explore risk factors that could be associated with the prevalence of genotype 2, genotypes 1 and 3 were grouped in the reference category, and adjusted prevalence ratio was calculated using modified Poisson regression, in a model that included the same variables as the multinomial logistical regression.
3. Results
From December 1st 2003 to January 28th 2008, 411 patients HCV-RNA positive were submitted to genotyping. Mean age was 41.1±12.0 years, 56.5% were men and most patients (73.9%) were from the health regional coordination of Passo Fundo, a medium size city in south of Brazil.
The proportions of genotypes were 41.5% (95% CI 37.9–48.1, n=183) for type 1 (55 subtype 1a and 41 subtype 1b), 19.3% (95% CI 15.0–23.6, n=85) for type 2, and 39.3% (95% CI 35.6–43.0, n=173) for type 3. There was a difference in genotype 2 distribution when comparing health centers, with higher genotype 2 prevalence in the largest city (22.7% versus 9.6%; P=0.007). Table 1 presents the genotype distribution according to sociodemographic characteristics and risk factors. Data regarding genotype, gender, and age were obtained for all patients. Some other variables were lost due to incomplete notification form filling. Genotype 1 was the most prevalent among men, while among women it was genotype 3 (P=0.028). Patients carrying genotype 2 were older (52.2 ± 12.8 years for type 2, versus 43.6 ± 11.2 years for type 1 and 45.6 ± 11.5 years for type 3; P<0,001), and the prevalence of nonwhite subjects was lower than in other groups (3.6% in type 2, versus 13.1% in type 1 and 6.6% in type 3). Among several established risk factors for HCV infection, use of intravenous and inhalation drugs, surgical treatment, and dental procedures were associated to the genotype (Table 2). On the multinomial regression, older age, history of dental procedure, and higher education increased the risk for infection by genotype 2 (Table 3). Adjusted prevalence ratios are shown in Figure 1. Dental procedure was associated with higher prevalence of genotype 2 independently of age, education and of which treatment center patient came from.
Sociodemographic characteristics of hepatitis C virus infected patients according to genotype.
Characteristics
N
*
Genotype 1
Genotype 2
Genotype 3
P value
N (%)
N (%)
N (%)
Male
249
116 (46.6)
40 (16.1)
93 (37.3)
0.028
Female
192
67 (34.9)
45 (23.4)
80 (41.7)
White color
389
152 (39.1)
81 (20.8)
156 (40.1)
0.012
Nonwhite color
38
24 (63.1)
3 (7.9)
11 (28.9)
Education
0.079
0–3 years
54
24 (44.4)
14 (25.9)
16 (29.6)
4–11 years
220
89 (40.5)
38 (17.3)
93 (42.3)
College
57
22 (38.6)
18 (31.6)
17 (29.8)
Age
441
<0.001
18–40 years
79 (51.1)
18 (11.6)
58 (37.4)
>40–60 years
92 (39.9)
51 (21.6)
93 (39.4)
>60 years
12 (24.0)
16 (32.0)
22 (44.0)
Genotype distribution according to risk factors among hepatitis C virus-infected patients from the countryside of southern Brazil (N and %).
Risk factors
N
*
Genotype 1
Genotype 2
Genotype 3
P value*
Blood transfusion
397
0.160
Yes
50 (36.5)
33 (24.1)
54 (39.4)
No
118 (45.4)
46 (17.7)
96 (36.9)
Use of IV medication
393
0.199
Yes
68 (41.7)
39 (23.9)
56 (34.4)
No
95 (41.3)
40 (17.4)
95 (41.3)
Acupuncture
393
0.726
Yes
4 (30.8)
3 (23.1)
6 (46.2)
No
163 (41.5)
79 (20.1)
151 (38.4)
Hemodialysis
390
0.510
Yes
4 (30.8)
2 (15.4)
7 (53.8)
No
157 (41.6)
77 (20.4)
143 (37.9)
Exposure to blood or organic secretions
391
0.119
Yes
26 (31.7)
19 (23.2)
37 (45.1)
No
137 (44.3)
58 (18.8)
114 (36.9)
Tatoo
393
0.207
Yes
25 (46.3)
6 (11.1)
23 (42.6)
No
138 (40.7)
73 (21.5)
128 (37.8)
Use of injection drugs
394
0.032
Yes
38 (53.5)
7 (9.9)
26 (36.6)
No
129 (39.9)
71 (22.0)
123 (38.1)
Surgical treatment
393
0.023
Yes
81 (39.5)
52 (25.4)
72 (35.1)
No
82 (43.6)
27 (14.4)
79 (42.0)
Piercing
393
0.643
Yes
4 (40.0)
1 (10.0)
5 (50.0%)
No
159 (41.5)
78 (20.4)
146 (38.1)
Inhalation drug
389
0.028
Yes
32 (53.3)
5 (8.3)
23 (38.3)
No
130 (39.5)
73 (22.2)
126 (38.3)
Dental procedure
394
0.010
Yes
72 (36.7)
51 (26.0)
73 (37.2)
No
92 (46.5)
28 (14.1)
78 (39.4)
Transplant
391
0.287
Yes
1 (25.0)
0 (0.0)
3 (75.0)
No
161 (41.6)
79 (20.4)
147 (38.0)
Percutaneous accident
389
0.979
Yes
7 (43.8)
3 (18.8)
6 (37.5)
No
154 (41.3)
75 (20.1)
144 (38.6)
Chi*-square test; IV: intravenous.
Risk factors for genotype 1 and for genotype 3 compared to genotype 2 in patients with HCV infection in the countryside of southern Brazil.
RR
95% CI
P
*
Genotype 1
Age
0.94
0.91–0.96
<0.001
Education
0–3 years
2.38
0.81–6.57
0.095
4–11 years
1.94
0.89–4.25
0.096
≥12 years
1
Dental procedure
Yes
0.37
0.19–0.70
0.002
No
1
Genotype 3
Age
0.95
0.92–0.97
<0.001
Education
0–3 years
1.98
0.69–5.73
0.206
4–11 years
2.69
1.21–5.98
0.016
≥12 years
1
Dental procedure
Yes
0.48
0.25–0.93
0.029
No
1
*Multinomial regression adjusted for age, education, skin color, and dental procedure.
Prevalence ratio for genotype type 2 in patients with hepatitis C in southern Brazil.
4. Discussion
In this study we observed prevalence of genotypes 1, 2, and 3 of 41.5%, 19.3%, and 39.2%, respectively, which are not the same as observed in other regions of the country and the world. A study conducted in Spanish health centers [7] described a higher proportion of genotype 1 (65.4%) and only 3.1% of genotype 2. In Poland [9] there is a genotype 1 percentage much similar to the one found in this study, but with a higher genotype 2 (37.8%) and a lower genotype 3 (23.4%) proportion. In south India genotype 1 was found in only 18.8% of population, and genotype 3 was higher (62.2%) than in this study [24]. Of 284 samples from the III National Health and Nutrition Examination Survey, conducted in North and Central America, 275 were genotyped [25]. As in our study, genotype 1 was the most common one, but with an even higher prevalence (78.2%; 1a = 51.6% and 1b = 26.6%). Genotypes 2 (12.7%; 2a = 2.9 and 2b = 9.8) and 3 (6.2%) were less common, and genotypes 4 and 6 were also detected (1.1% and 1.8%, resp.). In Latin America countries such as Argentina and Venezuela, genotypes 1 and 2 account for almost 90% of cases [13–15].
In Brazil (Table 4), a study [21] with 1.668 samples collected between 1995 and 2000 in laboratories from different regions detected genotypes 1 (64.9%), 2 (4.6%), 3 (30.2%), 4 (0.2%), and 5 (0.1%). Proportions of each genotype were significantly different according to each region, but genotype 1 was always the most common (51.2% to 74.1%). The south region showed a lower proportion of genotype 1, when compared to other regions (51.2% versus 57.0 to 74.1%, P=0.001), and a higher proportion of genotype 3 (40.3% versus 24.7 to 31.6%). This pattern of distribution is similar to the one we found in the present study. Another study [22] with patients from several healthcare centers in Brazil included more participants, being 81% from public institutions and 19% from private practice. Patients mean age was 46 years, 62% were male and 80% were white. Genotypes 1 (64%), 2 (1.3%), 3 (33%), and 4 (1.7%) were identified. Most patients were from the south and southeast regions, and only 4% were from the northeast. Once again, there is a higher proportion of genotype 3 in the south compared to north and northeast (44% versus 27% and 26%). Genotype 1 was found in 51% of samples from southeast region and in 71% of samples from the northeast. Genotype 2 was detected in only 2% of samples from northeast and southeast, and in 5% of samples from the south. In the central-west region the prevalence of genotype 2 was higher (11.4%), but it was still lower than the one we found in our study (19.3%), which included only countryside cities. Our findings also differ from two studies conducted in Porto Alegre, the capital of state. The first was a retrospective study with 400 patients under treatment [23] from 1999 to 2000, which described a similar genotype distribution among men and women and a low prevalence of genotype 2 (41.3% of genotype 1, 5.0% of genotype 2, and 53.7% of genotype 3). In the second study [6], genotype 1 was diagnosed in 81.5% of coinfected outpatients in a HIV/AIDS reference center of the Brazilian public health system and was associated with male gender. The study recorded only 1.7% of genotype 2. The higher prevalence of genotype 3 among women found in our study can be explained by the older age of this group, since genotype 3 showed a positive and independent association with age.
Proportional HCV genotype distribution according to Brazilian studies.
Study
N
Region
Genotypes (%)
1
2
3
4
5
Campiotto et al. [21]
85
North
74.1
1.2
24.7
0
0
237
Northeast
66.6
2.9
30.4
0
0
79
Center-west
57.0
11.4
31.6
0
0
1111
Southeast
59.6
3.8
28.4
0.3
0.2
176
South
51.2
8.0
40.3
0
0
1688
Total
64.9
4.6
30.2
0.2
0.1
Focaccia et al. [22]
121
Northeast
71.0
2.0*
27.0
NI
0
705
Southeast
72.0
2.0*
26.0
NI
0
522
South
51.0
5.0*
44.0
NI
0
1348
Total
64.0
1.3
33.0
1.7
0
Alves et al. [23]
400
Porto Alegre-RS
41.3
5.0
53.7
0
0
Wolff et al. [6]
173
Porto Alegre-RS
81.5
1.7
16.2
0
0
Genotype* 2 plus 4; NI: not informed.
In Venezuela, increasing genotype 2 prevalence was described, rising from 26% in 1994–96 to 41% in 2005-06 [15]. A study conducted in Yucatãn, Mexico [26], described a genotype 2 prevalence of 33.3% significantly associated with family history of liver disease. Factors positively associated with genotype 2 in our study were age, higher education, and history of dental procedures. These characteristics may indicate a higher socioeconomic level, suggesting a specific risk profile. Genotype 2 among patients from Passo Fundo may be associated to socioeconomic and cultural differences in comparison to other smaller cities in the region. Although dental treatment is a known risk factor for hepatitis B [27], dental procedures include surgical treatment which represents a potential for HCV transmission through contaminated injection equipment. Even oral cavity examination might be involved, since it was found that sharing personal hygiene objects might explain the transmission of HCV [6].
Viral load has crucial relevance on the viral transmission. On crude analysis, there was a statistically significant association between genotype and risk factors for HCV transmission, as the use of injection and inhalation drugs, surgical treatment and dental procedures. Despite infected patients with history of previous exposition to those factors being more commonly infected by genotype 1, genotype 2 was relatively more frequent in participants with history of dental procedure (26%) in comparison to other risk factors (Table 1). These findings differ from studies with drug users in Poland [9] and Siberia [28], which recorded association between dental procedures and HCV genotype 1. But it agrees with a study from Lybia that recorded high incidence of the genotype 2 after surgery and dental procedure [29].
HCV genotype is a predictive factor to antiviral treatment response. There are clear evidence [30] indicating that genotypes 1 and 4 are associated to poor interferon response, either in single therapy or combined with ribavirin, the opposite being true for genotypes 2 and 3 treated for 24 weeks. Best treatment results, measured by viral parameters, are reached within 48 weeks for patients with genotype 2 or 3, while patients with genotype 1 need one year of treatment. Therefore, long-term benefits of HCV treatment may be estimated based on the characteristics of the treated population.
Since HCV treatment has high costs and is provided by the public health care system for all Brazilian citizens, we believe that almost all HCV positive patients from that regional population were included in the studied sample, but they may be representative of the lower income population. Although disease register is mandatory, occasionally the form was incompletely filled, causing loss of epidemiologic information and a limitation of our study. The method limitation to identify genotype subtypes deserves mention, but this was not an aim of the study and it is still the method performed in the Brazilian health system and the only one offered by the public system, in the place where the study was conducted.
In conclusion, in a region from south Brazil the most common HCV genotype was type 1, followed by type 3, in accordance to previous reports, but the proportion of genotype 2 was higher than expected and was significantly associated to history of dental procedures and older age.
Conflict of Interests
The authors report no commercial association or any other potential conflict of interests.
Ethical Approval
Ethical approval was gained from Ethics Committee of Passo Fundo University.
BostanN.MahmoodT.An overview about hepatitis C: a devastating virus2010362911332-s2.0-7795064847010.3109/10408410903357455ArmstrongG. L.WasleyA.SimardE. P.McQuillanG. M.KuhnertW. L.AlterM. J.The prevalence of hepatitis C virus infection in the United States, 1999 through 20022006144107057142-s2.0-33646852746ShepardC. W.FinelliL.AlterM. J.Global epidemiology of hepatitis C virus infection2005595585672-s2.0-2394450601410.1016/S1473-3099(05)70216-4SyT.JamalM. M.Epidemiology of hepatitis C virus (HCV) infection20063241462-s2.0-33646238684World Health OrganizationHepatitis C—global prevalence2000751728WolffF. H.FuchsS. C.BarcellosN. N. T.de AlencastroP. R.IkedaM. L. R.BrandãoA. B. M.FalavignaM.FuchsF. D.Co-infection by Hepatitis C virus in HIV-infected patients in Southern Brazil: genotype distribution and clinical correlates2010552-s2.0-7795653645910.1371/journal.pone.0010494e10494EchevarríaJ. M.jmecheva@isciii.esLeónP.PozoF.AvellónA.Follow-up of the prevalence of hepatitis C virus genotypes in Spain during a nine-year period (1996–2004)2006241202510.1157/13083370Del Carmen Ramos-SánchezM.montealeku@gmail.comMartín-GilF. J.Changes in the distribution of hepatitis C virus (HCV) genotypes over the 1999 2010 period in Northern Valladolid, Spain201185222723010.1590/S1135-57272011000200010ChlabiczS.FlisiakR.KowalczukO.Wiercińska-DrapaloA.Pytel-KrolczukB.ProkopowiczD.ChyczewskiL.High prevalence of genotype 4 among hepatitis C virus-infected intravenous drug users in North-Eastern Poland20088046156182-s2.0-4054913069610.1002/jmv.21107MaieronA.Metz-GercekS.HacklF.LugerC.ZiachehabiA.StraussR.SchöflR.MittermayerH.Chronic hepatitis C in Austria, 1992–2006: genotype distribution and demographic factors2010158194922-s2.0-77950480177MicalessiM.GerardC.AmeyeL.PlasschaertS.BrochierB.VrankxR.Distribution of hepatitis C virus genotypes among injecting drug users in contact with centers in Belgium, 2004-2005200880640645Burguete-GarcíaA. I.Conde-GonzálezC. J.Jiménez-MéndezR.Juárez-DíazY.Meda-MonzónE.Torres-PovedaK.Madrid-MarinaV.Hepatitis C seroprevalence and correlation between viral load and viral genotype among primary care clients in Mexico201153, supplement 1S7S12RéV.ContigianiM.YoshidaC. F. T.LampeE.Identification of hepatitis C virus subtype 2c by sequencing analysis in patients from Córdoba, Argentina200710289959982-s2.0-38149077922ReV.LampeE.YoshidaC. F.De OliveiraJ. M.Lewis-XimenezL.SpinsantiL.ElbarchaO.ContigianiM.Hepatitis C virus genotypes in Cordoba, Argentina. Unexpected high prevalence of genotype 220036332052102-s2.0-0037622542PujolF. H.LoureiroC. L.Replacement of hepatitis C virus genotype 1b by genotype 2 over a 10-year period in Venezuela20074155185202-s2.0-3424733594210.1097/01.mcg.0000248010.55149.ceOliveira-FilhoA. B.PimentaA. S. C.RojasM. F. M.ChagasM. C. M.CrescenteJ. A. B.CrespoD. M.LemosJ. A. R.Prevalence and genotyping of hepatitis C virus in blood donors in the state of Pará, Northern Brazil201010511031062-s2.0-76749160390ViganiA. G.PavanM. H.TozzoR.GonçalesE. S. L.FeltrinA.FaisV. C.LazariniM. S. K.GonçalesN. S. L.GoncalesJ. F. L.Comparative study of patients with chronic hepatitis C virus infection due to genotypes 1 and 3 referred for treatment in southeast Brazil20088, article 1642-s2.0-5814934522510.1186/1471-2334-8-164Da SilvaC. M. D.CostiC.KrugL. P.RamosA. B.GrandiT.GandolfiV. L.MenezesM. E.OcamposM.NielC.RossettiM. L. R.High proportion of hepatitis C virus genotypes 1 and 3 in a large cohort of patients from Southern Brazil200710278678702-s2.0-37049030011DavidsonF.SimmondsP.FergusonJ. C.JarvisL. M.DowB. C.FollettE. A. C.SeedC. R. G.KrusiusT.LinC.MedgyesiG. A.KiyokawaH.OlimG.DuraisamyG.CuypersT.SaeedA. A.TeoD.ConradieJ.KewM. C.YapP. L.Survey of major genotypes and subtypes of hepatitis C virus using RFLP of sequences amplified from the 5' non-coding region1995765119712042-s2.0-0029000103FornsX.CostaJ.HCV virological assessment2006441S35S392-s2.0-3014443532410.1016/j.jhep.2005.11.010CampiottoS.PinhoJ. R. R.CarrilhoF. J.Da SilvaL. C.SoutoF. J. D.SpinelliV.PereiraL. M. M. B.CoelhoH. S. M.SilvaA. O.FonsecaJ. C.RosaH.LacetC. M. C.BernardiniA. P.Geographic distribution of hepatitis C virus genotypes in Brazil200538141492-s2.0-14044259996FoccaciaR.BaraldoD. C. M.FerrazM. L. G.MartinelliA. L. C.GonçalvesF. R.Jr. PedroM. L. A.Demographic and antropometrical analysis and genotype distribution of cronic pacientes treated in public and private reference centers in Brazil20048348355AlvesA. V.De AzevedoA. P. D. C.PerinC.RamosG. Z.BrandãoA. B. D. M.De MattosA. A.De AlmeidaP. R. L.Interferon-α and ribavirin therapy on chronic hepatitis C virus infection: the experience of Rio Grande do Sul State Health Department, Brazil20034042272322-s2.0-2442417839RaghuramanS.ShajiR. V.SridharanG.RadhakrishnanS.ChandyG.RamakrishnaB. S.AbrahamP.Distribution of the different genotypes of HCV among patients attending a tertiary care hospital in south India200326161692-s2.0-003727168110.1016/S1386-6532(02)00025-2NainanO. V.AlterM. J.Kruszon-MoranD.GaoF. X.XiaG.McQuillanG.MargolisH. S.Hepatitis C virus genotypes and viral concentrations in participants of a general population survey in the United States200613124784842-s2.0-3374654687010.1053/j.gastro.2006.06.007García-MontalvoB. M.Galguera-ColoradoP. L.Distribution of hepatitis C virus genotypes, risk factors and liver disease in patients from Yucatán, México2008743453492-s2.0-56749165425ArtiniM.ScoarughiG. L.PapaR.DolciG.De LucaM.OrsiniG.PappalardoS.CostertonJ. W.SelanL.Specific anti cross-infection measures may help to prevent viral contamination of dental unit waterlines: a pilot study20083654674712-s2.0-5654912077210.1007/s15010-008-7246-5ShustovA. V.KochnevaG. V.SivolobovaG. F.GrazhdantsevaA. A.GavrilovaI. V.AkinfeevaL. A.RakovaI. G.AleshinaM. V.BukinV. N.OrlovskyV. G.BespalovV. S.RobertsonB. H.NetesovS. V.Molecular epidemiology of the hepatitis C virus in Western Siberia20057733823892-s2.0-2584444967710.1002/jmv.20467AlashekW. A.AltagdiM.Risk factors and genotypes of hepatitis C virus infection in Libyan patients200834Torres-PuenteM.CuevasJ. M.Jiménez-HernándezN.BrachoM. A.García-RoblesI.WrobelB.CarnicerF.Del OlmoJ.OrtegaE.MoyaA.González-CandelasF.fernando.gonzalez@uv.esGenetic variability in hepatitis C virus and its role in antiviral treatment response200815318819910.1111/j.1365-2893.2007.00929.x