Distribution Of Hepatitis C Virus Subtypes Research Articles

Epidemiology of Hepatitis C Virus in HIV Patients from West Mexico: Implications for Controlling and Preventing Viral Hepatitis.

The complex epidemiology of hepatitis C virus (HCV) infection among human immunodeficiency virus (HIV) patients in West Mexico remains poorly understood. Thus, this study aimed to investigate the HCV prevalence, HCV-associated risk factors, and HCV genotypes/subtypes and assess their impacts on liver fibrosis in 294 HIV patients (median age: 38 years; 88.1% male). HCV RNA was extracted and amplified by PCR. Hepatic fibrosis was assessed using three noninvasive methods: transient elastography (TE), the aspartate aminotransferase (AST)-to-platelets ratio index score (APRI), and the fibrosis-4 score (FIB4). Patients with liver stiffness of ≥9.3 Kpa were considered to have advanced liver fibrosis. HCV genotypes/subtypes were determined by line probe assay (LiPA) or Sanger sequencing. The prevalence of HIV/HCV infection was 36.4% and was associated with injection drug use (odds ratio (OR) = 13.2; 95% confidence interval (CI) = 5.9-33.6; p < 0.001), imprisonment (OR = 3.0; 95% CI = 1.7-5.4; p < 0.001), the onset of sexual life (OR = 2.6; 95% CI = 1.5-4.5; p < 0.001), blood transfusion (OR = 2.5; 95% CI = 1.5-4.2; p = 0.001), tattooing (OR = 2.4; 95% CI = 1.4-3.9; p = 0.001), being a sex worker (OR = 2.3; 95% CI = 1.0-5.4; p = 0.046), and surgery (OR = 1.7; 95% CI = 1.0-2.7; p = 0.042). The HCV subtype distribution was 68.2% for 1a, 15.2% for 3a, 10.6% for 1b, 3.0% for 2b, 1.5% for 2a, and 1.5% for 4a. The advanced liver fibrosis prevalence was highest in patients with HIV/HCV co-infection (47.7%), especially in those with HCV subtype 1a. CD4+ counts, albumin, direct bilirubin, and indirect bilirubin were associated with liver fibrosis. In conclusion, HCV infection had a significant impact on the liver health of Mexican HIV patients, highlighting the need for targeted preventive strategies in this population.

Complicated HCV subtype expansion among drug users in Guangdong province, China

Guangdong Province is one of the most developed and populous provinces in southern China. The subtype situation of hepatitis C virus (HCV) in Guangdong remains unknown. The aim of this study was to investigate and estimate the HCV subtypes in drug users (DU) using a city-based sampling strategy to better understand the characteristics of HCV transmission in Guangdong. Archived plasma samples (n = 1074) from DU who were anti-HCV positive in 2014 were selected randomly from 20 cities in Guangdong Province. Subtypes were determined based on core and/or E1 sequences using phylogenetic analysis. The distributions of HCV subtypes in DU and different regions were analyzed. A total of 8 genotypes were identified. The three main HCV subtypes in DU in Guangdong were 6a (63.0%), 3a (15.2%), and 3b (11.8%). Significant differences were discovered among different registered residency and regions but not among genders, marital status, education level, or drug use patterns. HCV subtype 3b was significantly higher in Guangdong residents than in non-Guangdong residents. In contrast, HCV subtype 6a was significantly lower in Guangdong residents than in non-Guangdong residents. Subtype 1b in eastern Guangdong (eastern) was significantly lower, while 6a was significantly higher when compared with other regions. Subtype 3a in the Pearl River Delta (PRD) region was significantly higher, while 3b was significantly lower when compared with other regions. In western Guangdong, HCV subtype 3a was significantly lower when compared with other regions. Additionally, in northern Guangdong subtypes 1b and 3b were significantly higher, while 6a was significantly lower when compared with other regions. Our study revealed the diversity and distribution of HCV subtypes in DU in nearly all the cities in Guangdong. The results provide essential information that will allow the establishment of specific intervention strategies that may help prevent HCV transmission.

Identification of a New HCV Subtype 6xg Among Injection Drug Users in Kachin, Myanmar.

Characterizing hepatitis C virus (HCV) genetic diversity not only allows us to trace its origin and evolutionary history, but also provides valuable insights into diagnosis, prevention and therapy of HCV infection. Although eight HCV genotypes and 86 subtypes have been classified, there are still some HCV variants that need to be assigned. The genotype 6 is the most diverse HCV genotype and mainly prevalent in Southeast Asia. In this study, we identified a new HCV subtype 6xg from injection drug users (IDUs) in Kachin, Myanmar. A distinctive feature of 6xg from other subtypes of the genotype 6 was a Lys insertion in NS5A gene, which changes the RRKR/K motif into RRKKR/K. Bayesian analyses showed that HCV 6xg originated during 1984–1988, and experienced a rapid population expansion during 2005–2009. We characterized HCV subtype profile among IDUs in this region, and detected six HCV subtypes, including 1a (12.0%), 3a (12.0%), 3b (24.0%), 6n (16.0%), 6xa (20.0%), and 6xg (12.0%). Importantly, we found that HCV subtype distribution in Kachin was very similar to that in Dehong prefecture of Yunnan, but very distinct from those in other regions of Myanmar and Yunnan, indicating that the China–Myanmar border region shared a unique HCV subtype pattern. The appearance of 6xg and the unique HCV subtype profile among IDUs in the China–Myanmar border region have significant epidemiological and public health implications.

Variation in Hepatitis C Virus Subtype Distribution during 20 Years in Venezuela

Objective: Hepatitis C virus (HCV) infection is a public health problem and a major cause of chronic hepatitis. This virus exhibits a great genetic variability, with 8 genotypes and numerous subtypes. The aim of this study was to evaluate the fluctuations of HCV subtypes during 2 decades in Venezuela. Methods: HCV genotypes were determined by direct sequencing of the 5ʹ-noncoding region in 392 isolates circulating in patients attended during the years 2014–2015. HCV subtype assignment was confirmed in a subset of samples (n = 24) by partial sequencing of the NS5B region. The genotype distribution was compared with the one observed in a previous study of patients followed up during the years 1994–1996 and 2005–2006. Results: Some variation was observed in the HCV genotype distribution over these 20 years. HCV genotype 1b prevalence was reduced significantly from 1994–1995 to 2004–2005, as previously described, and then remained constant. During the last 10 years, a significant decrease of HCV subtype 2b (36/237 in 2005–2006 vs. 24/392 in 2014–2015, p < 0.001) was observed. Patients infected with HCV G2acj were significantly older than the ones infected with G1 (53 vs. 47 years, p = 0.004), and male sex was significantly more prevalent among G3a-infected patients compared to the other ones (71 vs. 47%, p = 0.047). Conclusions: Fluctuations in HCV subtype distribution have been observed over 2 decades in Venezuela. Different major mode of transmission and susceptibility to the available HCV treatment during each period might be playing a role in the observed fluctuations in HCV subtype distribution.

Hepatitis C virus genotype diversity and distribution among methadone maintenance treatment patients in Jiangsu, China

Background: Heroin users are vulnerable and represent a highly-infected reservoir for hepatitis C virus (HCV) infection. This study investigated HCV prevalence and genotypes distribution among heroin users who received methadone maintenance treatment (MMT) in Jiangsu.Methods: From June to December in 2016, a total of 534 patients among nine MMT clinics in six regions of Jiangsu were enrolled, with their demographic characteristics collected and serum samples tested for HCV antibody. 395 samples were seropositive and furthered to RNA extraction. HCV NS5B region fragments were amplified and subsequently sequenced.Results: Among HCV seropositive samples, 240 were characterized by NS5B partial sequences and classified into four genotypes (GPs) and eight subtypes. HCV GP3 predominated and accounted for 66.3%, followed by GP1 (27.5%), GP6 (4.2%) and GP2 (2.1%). HCV subtypes 3b (41.7%) and 3a (24.6%) were the most common subtypes. None of the demographic characteristics showed a significant difference when comparing with HCV genotypes. The geographic feature shown GPs in six regions were the same, but the frequency of subtypes exhibited regional divergence. Phylogenetic analyses demonstrated that 3b had become a local endemic in Jiangsu.Conclusion: The distribution of HCV subtypes among heroin users in Jiangsu province was complex. The data could provide more precise estimates for HCV prevalence and genotype distribution as well as heroin users of Jiangsu province.

High HCV subtype heterogeneity in a chronically infected general population revealed by high-resolution hepatitis C virus subtyping

ObjectivesThis study aimed to characterize the chronically infected general hepatitis C virus (HCV) population in Barcelona using a highly sensitive subtyping method that can identify the 67 recognized HCV subtypes and diagnose mixed infection by various genotypes/subtypes in a single individual. The resulting information has implications for selecting optimal direct-acting antiviral (DAA) treatment for each patient and establishing public healthcare policies in our setting. MethodsConsecutive HCV patients (treatment-naïve or interferon-based failures) attending Vall d'Hebron Hospital outpatient clinics from February 2015 to May 2016 (N=1473) were included in the study. Patient samples were characterized using HCV subtyping by next-generation ultra-deep pyrosequencing. ResultsThe following genotypes (G) were found: G1 (1126/1473 (76.4%)), G4 (145/1473 (9.8%)), G3 (135/1473 (9.2%)), G2 (51/1473 (3.5%)), and G5 (1/1473 (0.1%)). Twenty-two subtypes were seen: 1b (790/1473 (53.6%)), 1a (332/1473 (22.5%)), 3a (133/1473 (9.0%)), 4d (105/1473 (7.1%)), 4a (29/1473 (2.0%)), and 2c (25/1473 (1.7%)), with 16 low-prevalence subtypes accounting for the remaining 3.0% (44/1473). There was a worrisome 1.0% (15/1473) of mixed infections. G2 (51/1473 (3.5%)) showed a high level of heterogeneity. Analyses by age groups showed a predominance of G1b over G1a (428/506 (84.6%) vs. 24/506 (4.7%)) in patients born before 1950 (N=506/1473), and similar percentages of these subtypes in those born between 1951 and 1975 (N=834/1473) (315/834, 37.8% vs. 266/834, 31.9%) and after 1976 (N=133/1473) (47/133, 35.3% vs. 42/133, 31.6%). ConclusionsSubtype distribution showed a higher level of heterogeneity than was expected, particularly for G2. Prevalence of mixed infections was around 1%. HCV subtype distribution related to patient age group suggested that patients born from 1936 to 1975 in our setting should undergo screening for the infection. Next-generation sequencing enabled better classification of candidates for DAA-based treatment.

High Rates of Hepatitis B Virus (HBV), Hepatitis C Virus (HCV), and Human Immunodeficiency Virus Infections and Uncommon HBV Genotype/Subtype and HCV Subtype Distributions among Transgender Individuals in Surabaya, Indonesia.

Transgender people are at a high risk for sexually transmitted viruses such as hepatitis B virus (HBV) and human immunodeficiency virus (HIV). Moreover, Indonesia has a moderate-to-high rate of HBV infection and rapid epidemic growth of HIV infection; hepatitis C virus (HCV) infection can co-occur with HBV and HIV infections. In this study, 10 of 107 individuals (9.3%) were positive for HBV surface antigen (HBsAg) and/or HBV DNA, whereas 19 of 101 individuals (18.8%) with negative results for HBsAg were positive for HBV core antibody (anti-HBc). Seven of the 107 individuals (6.5%) were anti-HCV positive, and 16 of the 100 tested samples (16.0%) were HIV positive. Genotype and subtype analyses of all 10 HBV DNA (6 HBsAg positive and 4 anti-HBc positive) strains showed that 3 were of the HBV genotype/HBsAg subtype C/adrq+, one was of C/adw2, and 5 were of B/adw2. The HCV subtype distribution showed that 33.3% were of HCV-1b, and 66.7% were of HCV-3k (n = 6). These distributions differed from those found in the general population of Surabaya, Indonesia. Interestingly, HIV subtype analysis showed a high prevalence of HIV, with possible recombinants of CRF01_AE and subtype B.

Multiple Introduction and Naturally Occuring Drug Resistance of HCV among HIV-Infected Intravenous Drug Users in Yunnan: An Origin of China's HIV/HCV Epidemics.

BackgroundThe human immunodeficiency virus 1 (HIV-1) epidemic in China historically stemmed from intravenous drug users (IDUs) in Yunnan. Due to a shared transmission route, hepatitis C virus (HCV)/HIV-1 co-infection is common. Here, we investigated HCV genetic characteristics and baseline drug resistance among HIV-infected IDUs in Yunnan.MethodsBlood samples of 432 HIV-1/HCV co-infected IDUs were collected from January to June 2014 in six prefectures of Yunnan Province. Partial E1E2 and NS5B genes were sequenced. Phylogenetic, evolutionary and genotypic drug resistance analyses were performed.ResultsAmong the 293 specimens successfully genotyped, seven subtypes were identified, including subtypes 3b (37.9%, 111/293), 3a (21.8%, 64/293), 6n (14.0%, 41/293), 1b (10.6%, 31/293), 1a (8.2%, 24/293), 6a (5.1%, 15/293) and 6u (2.4%, 7/293). The distribution of HCV subtypes was mostly related to geographic location. Subtypes 3b, 3a, and 6n were detected in all six prefectures, however, the other four subtypes were detected only in parts of the six prefectures. Phylogeographic analyses indicated that 6n, 1a and 6u originated in the western prefecture (Dehong) and spread eastward and showed genetic relatedness with those detected in Burmese. However, 6a originated in the southeast prefectures (Honghe and Wenshan) bordering Vietnam and was transmitted westward. These subtypes exhibited different evolutionary rates (between 4.35×10−4 and 2.38×10−3 substitutions site-1 year-1) and times of most recent common ancestor (tMRCA, between 1790.3 and 1994.6), suggesting that HCV was multiply introduced into Yunnan. Naturally occurring resistance-associated mutations (C316N, A421V, C445F, I482L, V494A, and V499A) to NS5B polymerase inhibitors were detected in direct-acting antivirals (DAAs)-naïve IDUs.ConclusionThis work reveals the temporal-spatial distribution of HCV subtypes and baseline HCV drug resistance among HIV-infected IDUs in Yunnan. The findings enhance our understanding of the characteristics and evolution of HCV in IDUs and are valuable for developing HCV prevention and management strategies for this population.

The Molecular Epidemiological Study of HCV Subtypes among Intravenous Drug Users and Non-Injection Drug Users in China.

BackgroundMore than half of intravenous drug users (IDUs) in China suffer from the Hepatitis C virus (HCV). The virus is also more prevalent in non-injection drug users (NIDUs) than in the general population. However, not much is known about HCV subtype distribution in these populations.MethodsOur research team conducted a cross-sectional study in four provinces in China. We sampled 825 IDUs and 244 NIDUs (1162 total), genotyped each DU’s virus, and performed a phylogenetic analysis to differentiate HCV subtypes.ResultsNucleic acid testing (NAT) determined that 82% percent (952/1162) of samples were HCV positive; we subtyped 90% (859/952) of these. We found multiple HCV subtypes: 3b (249, 29.0%), 3a (225, 26.2%), 6a (156, 18.2%), 1b (137, 15.9%), 6n (50, 5.9%), 1a (27, 3.1%), and 2a (15, 1.7%). An analysis of subtype distributions adjusted for province found statistically significant differences between HCV subtypes in IDUs and NIDUs.DiscussionHCV subtypes 3b, 3a, 6a, and 1b were the most common in our study, together accounting for 89% of infections. The subtype distribution differences we found between IDUs and NIDUs suggested that sharing syringes was not the most likely pathway for HCV transmission in NIDUs. However, further studies are needed to elucidate how NIDUs were infected.

Analysis on genotypes of hepatitis C virus among intravenous drug users in Kunming, Yunnan

To investigate the distribution of hepatitis C virus (HCV) subtypes among intravenous drug users (IDUs) in Kunming, Yunnan province, in 2014. A total of 276 plasma samples were collected from IDUs in Kunming during April 2014 -July 2014, in which 199 plasma samples were tested to be HCV antibody positive. For the HCV antibody positive samples, HCV E1E2 genes and NS5B genes were amplified by using nested-polymerase chain reaction (PCR). After sequencing, the HCV subtypes were determined through phylogenetic analysis. Based on the phylogenetic trees of E1E2 gene and NS5B gene fragments, a total of 125 samples were genotyped. 3b was the predominant subtype (48.8%,61/125), followed by 3a (30.4%, 38/125), 6n (14.4%, 18/125), 6a (3.2%, 4/125) and 1b (3.2%, 4/125). The distributions of HCV subtypes by sex, marital status, ethnic group and HIV-1 infection status showed no statistical differences. However, the distribution of HCV subtypes by age showed statistical difference, the diversity of HCV subtypes was found in age group <45 years. The genetic distances of 3a, 3b and 6a on E1E2 and NS5B were larger than those of 1b and 6n. For genotype 3, the genetic distances of 3b on E1E2 and NS5B were larger than those of 3a. Five HCV subtypes were found among IDUs in Kunming, HCV subtypes 3b and 3a were predominant, which have circulated in this population for long time.

Hepatitis C virus genotypes in China: a systematic review

To provide information on the geographical distribution of hepatitis C virus (HCV) genotype and subtypes in the Chinese population. A comprehensive search was carried out in CHKD (China Hospital Knowledge Database), Wanfang (Chinese), CBMDisc and PubMed databases to identify all the papers being published on HCV genotypes/serotypes and subtypes in China. All studies were grouped according to the sites, period and objects of the studies, to analyse the distribution of HCV genotype. A total of 140 studies were included in this Meta-analysis program, which contained 168 records. We found that the predominate genotypes in China were 1b and 2a subtype, and the distributions of HCV subtypes were different in the western or southern parts of the country. Subtypes 3a, 3b and 6a had been significantly increased along with the decrease of subtypes 1b and 2a. There were various HCV subtypes among injection drug users with subtypes 3a, 3b and 6a found among them. The distribution of HCV genotypes and subtypes in the Chinese population had changed significantly.

Molecular characterization, distribution, and dynamics of hepatitis C virus genotypes in blood donors in Colombia

Hepatitis C virus (HCV) is a frequent cause of acute and chronic hepatitis and a leading cause for cirrhosis of the liver and hepatocellular carcinoma. HCV is classified in six major genotypes and more than 70 subtypes. In Colombian blood banks, serum samples were tested for anti-HCV antibodies using a third-generation ELISA. The aim of this study was to characterize the viral sequences in plasma of 184 volunteer blood donors who attended the "Banco Nacional de Sangre de la Cruz Roja Colombiana," Bogotá, Colombia. Three different HCV genomic regions were amplified by nested PCR. The first of these was a segment of 180 bp of the 5'UTR region to confirm the previous diagnosis by ELISA. From those that were positive to the 5'UTR region, two further segments were amplified for genotyping and subtyping by phylogenetic analysis: a segment of 380 bp from the NS5B region; and a segment of 391 bp from the E1 region. The distribution of HCV subtypes was: 1b (82.8%), 1a (5.7%), 2a (5.7%), 2b (2.8%), and 3a (2.8%). By applying Bayesian Markov chain Monte Carlo simulation, it was estimated that HCV-1b was introduced into Bogotá around 1950. Also, this subtype spread at an exponential rate between about 1970 to about 1990, after which transmission of HCV was reduced by anti-HCV testing of this population. Among Colombian blood donors, HCV genotype 1b is the most frequent genotype, especially in large urban conglomerates such as Bogotá, as is the case in other South American countries.

Ruolo del sequenziamento diretto nella tipizzazione di HCV-RNA a fini clinico-epidemiologici

Background/Aims: Genotyping and subtyping of hepatitis C virus (HCV) is epidemiologically and clinically relevant to prognosis and therapeutical management of HCV infection.Aim was to study the feasibility of an “in house” direct sequencing method for the genotyping and subtyping of HCV strains compared with a commercially available genotyping assay (Inno-LiPA,VERSANT® HCV Genotype 2.0 Assay, Bayer). Methods: 74 clinical plasma samples cross-representing HCV genotypes 1 to 5 typed with the line probe assay Inno-LiPA (LiPA) were subjected to a laboratory-developed 5’UTR direct sequencing protocol (5’UTR Seq).A NS5B direct sequencing protocol (NS5B Seq) was apply to 23/74 samples (17 negative by the 5’UTR).Two libraries of 5’UTR and NS5B HCV prototypes were constructed; BioEdit 7.0.0 and ClustalW were used for alignments and phylogenetic analysis. Results: 5’UTR Seq typed 47/74 LiPA positive samples (64%). Concordance between the two assays was 91% (43/47) and 72% (31/43) for HCV genotyping and subtyping, respectively. LiPA and 5’UTR Seq discordant samples were typed by NS5B Seq. NS5B Seq typed 13/17 samples negative with 5’UTR Seq.All genotypes and subtypes detected with NS5B Seq were concordant with LiPA. 5’UTR and NS5B direct sequencing pointed out a wider HCV subtype distribution than LiPA for genotype 1, 2 and 4. By the combination of 5’UTR and NS5B direct sequencing, 81% (60/74) of LiPA positive samples were typed. Conclusion: HCV typing and subtyping with the line probe assay Inno-LiPA is highly recommended for clinical purposes.A more detailed HCV typing for epidemiologic purposes can by achieved by the direct sequencing of a region with a moderate degree of genetic variability such as NS5B. HCV NS5B analysis is more efficient in resolving viral strain genetic variability than direct sequencing of a highly conserved region such as 5’UTR.

Analysis of the 5′ Noncoding Region versus the NS5b Region in Genotyping Hepatitis C Virus Isolates from Blood Donors in France

The 5' noncoding region (5' NCR) of the hepatitis C virus (HCV) has become the standard for genotyping even though several reports show that its use can result in classification errors. The purpose of this study was to perform genotyping based on sequence analysis of the NS5b region in a set of 357 HCV strains isolated from blood donors in France in 2002 and 2003. Results were compared with those previously obtained using 5' NCR analysis, and HCV subtype distribution was reevaluated. Twenty-six of 120 strains (approximately 22%) initially identified as genotype 1b by 5' NCR region sequence analysis were reclassified as genotype 1a by NS5b region sequence analysis. Similarly, 14 of 23 strains (approximately 61%) initially identified as 2a/2c were reclassified as non-2a and non-2c subtypes, and 12 of 22 strains (approximately 45%) initially identified as 4c/4d subtypes were reclassified as non-4c and non-4d subtypes. Sequence analysis of the NS5b region also revealed 5 putative new subtype 2 variants and 2 putative new subtype 4 variants. Although these findings demonstrated full agreement between 5' NCR and NS5b sequence analysis with regard to type classification, genotyping based on phylogenetic analysis of the NS5b region is more accurate for subtype determination than genotyping based on analysis of the 5' NCR. Sequence analysis of the NS5b region is mandatory for epidemiologic studies.

Prevalence and Distribution of Hepatitis C Subtypes in Patients with Opioid Dependence

Aim and Setting: The drug addiction out-patient clinic at the University Hospital for Psychiatry in Vienna performed a study to identify the prevalence of hepatitis C virus (HCV) infections in a group of opiate-dependent patients, to detect the distribution of HCV subtypes and to calculate the comorbidity of human immunodeficiency virus (HIV) and hepatitis B virus (HBV). Design and Participants: We consecutively investigated unselected patients (n = 173) during an observation period of 2 months with the diagnosis of opioid dependence (DSM-IV: 304.0) and polysubstance dependence (DSM-IV: 304.9). Measurements: Blood was investigated focusing on liver enzymes and on viral status including HIV, hepatitis B and hepatitis C, followed by subtyping of the virus. Findings: In 80.3% hepatitis C antibodies were found, 66.5% were HCV RNA (PCR) positive. 3a was the most frequent subtype (35.6%), followed by 1a (28.8%) and 1b (22.0%). Four patients had both subtypes 1a and 1b (6.8%), 3 were 2b positive (5.1%) and 1 patient had subtypes 2a/2c (1.7%). No significant difference in aspartate (AST) and alanine aminotransferases (ALT) concerning the different subtypes (AST: p = 0.290; ALT: p = 0.260) could be calculated; 11.6% showed co-infection with HIV, 2 patients had a chronic infection with hepatitis B. Conclusions: The rate of HCV infection in substance-dependent patients at our drug addiction out-patient clinic is extremely high. The distribution of subtypes showed a relatively homogeneous distribution of the types 1a, 1b and 3a. The recommended therapy with α-interferon should be initiated in drug-dependent patients under considerations of an enrollment in oral maintenance with synthetic opioids.

Distribution of the different subtypes of hepatitis C virus in Japan and the effects of interferon: a nationwide survey.

Interferon (IFN) is now commonly used for the treatment of type C hepatitis; however, its effects differ depending upon the subtype of hepatitis C virus (HCV) being treated. It has been recently confirmed in many studies in Japan that the effectiveness of IFN treatment is poor in patients having type 1b and better in patients having type 2a HCV. However, the effects of IFN treatment on other subtypes of HCV were not clear because of the small number of patients in each hospital. In the present study, the effects of IFN treatment in patients with other HCV subtypes were analysed from nationwide data collected in Japan using a standard questionnaire. From this questionnaire, local differences in the distribution of HCV subtypes in Japan were also analysed. A standard questionnaire, consisting of questions about the number of patients with chronic type C hepatitis with different HCV subtypes and the number of patients showing different responses to IFN treatment, was sent to over 40 study groups in Japan. Answers to the questionnaire concerning HCV subtypes and the effects of IFN treatment were obtained from 26 and 22 hospitals, respectively, throughout Japan. The incidence of HCV type 1b was highest in the Kinki area (south-central Japan). The incidence of type 1b HCV decreased in parallel with distance from this area. The mortality rates of hepatic cancer in different areas were significantly correlated with the incidence of HCV type 1b. The efficacy of IFN treatment was significantly better for both types 2a and 2b HCV than for type 1b HCV; the efficacy of IFN treatment was poor in the mixed type of 1b and 2a and tended to be better in type 1a. The efficacy of IFN treatment for other types of HCV was also better. These results indicate that there are local differences in the distribution of HCV subtypes in Japan and that these differences may be closely associated with the clinical features of HCV-related liver disease. The efficacy of IFN treatment was significantly poorer in patients with the 1b-related type HCV than in patients with other types of HCV.