Genotypic distribution of hepatitis C virus in different regions of Thailand

Prevalence of HCV genotypes and subtypes in Southeast Asia: A systematic review and meta-analysis

Known for its high genetic diversity and variation in genotypic presence in different regions of the world, hepatitis C virus (HCV) is estimated to infect about 71 million people globally. Selection of an appropriate therapeutic regimen largely depends on the identification of the genotype responsible for the infection. This systematic review and meta-analysis was conducted to provide a comprehensive view of HCV genotype and subtype distribution in Southeast Asia (SEA). The review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA). We searched five databases without year and language restrictions. Data from 90 eligible studies involving 15,089 genotypes and 9,646 subtypes representing 10 SEA countries were analyzed. The pooled estimates showed that genotype 1 (46.8%) [95% CI, 43.2–50.4; I² = 92.77%; p < 0.001] was the most dominant HCV genotype in the region, followed by genotype 3 (23.1%) [95% CI, 19.4–27.2; I² = 93.03%; p < 0.001], genotype 6 (16.5%) [95% CI, 13.8–19.6], genotype 2 (4.6%) [95% CI, 3.5–5.9], genotype 4 (1.1%) [95% CI, 0.7–1.5] and genotype 5 (0.8%) [95% CI, 0.4–1.3]. Philippines had the highest prevalence of genotypes 1 and 2. Genotype 6 became more prevalent after year 2000. Over 40 different subtypes were identified, with subtypes 1b (26.3%), 1a (21.3%), and 3a (14.3%) being the most prevalent of all the reported subtypes. Although on a global scale, genotype 6 is considered highly prevalent in SEA, evidence from this study reveals that it is the third most prevalent genotype within the region.

Molecular evolution of hepatitis C virus in China: A nationwide study

The evolutionary and epidemic history and the regional differences of hepatitis C virus (HCV) are complex and remain unclear in the vast territory China. Here we recruited 1540 HCV-RNA positive patients sampled in 29 provinces across whole China, which is the largest sample capacity and the most comprehensive geographic coverage of China to our knowledge. 1b, 2a, 3b, 6a and 3a were the major subtypes in China. 1b was the most predominant subtype which presented in every province. The second most predominant subtype, 2a, appeared to concentrate in the north of China. Subtypes 3a and 3b were mainly found in the Southwest region, while 6a was restricted in the South region. We further estimated the origins of the dominating subtypes and discovered for the first time that a Chinese-specific transmission pattern for some strains of subtype 2a which was restricted in north China, and Chinese subtype 3b originated from Thailand.

Decreasing Hepatitis C Virus Infection in Thailand in the Past Decade: Evidence from the 2014 National Survey

Hepatitis C virus (HCV) infection affects ≥ 180 million individuals worldwide especially those living in developing countries. Recent advances in direct-acting therapeutics promise effective treatments for chronic HCV carriers, but only if the affected individuals are identified. Good treatment coverage therefore requires accurate epidemiological data on HCV infection. In 2014, we determined the current prevalence of HCV in Thailand to assess whether over the past decade the significant number of chronic carriers had changed. In total, 5964 serum samples from Thai residents between 6 months and 71 years of age were obtained from 7 provinces representing all 4 geographical regions of Thailand and screened for the anti-HCV antibody. Positive samples were further analyzed using RT-PCR, sequencing, and phylogenetic analysis to identify the prevailing HCV genotypes. We found that 56 (0.94%) samples tested positive for anti-HCV antibody (mean age = 36.6±17.6 years), while HCV RNA of the core and NS5B subgenomic regions was detected in 23 (41%) and 19 (34%) of the samples, respectively. The seropositive rates appeared to increase with age and peaked in individuals 41-50 years old. These results suggested that approximately 759,000 individuals are currently anti-HCV-positive and that 357,000 individuals have viremic HCV infection. These numbers represent a significant decline in the prevalence of HCV infection. Interestingly, the frequency of genotype 6 variants increased from 8.9% to 34.8%, while the prevalence of genotype 1b declined from 27% to 13%. These most recent comprehensive estimates of HCV burden in Thailand are valuable towards evidence-based treatment coverage for specific population groups, appropriate allocation of resources, and improvement in the national public health policy.

Epidemiology of hepatitis C virus genotypes in northeastern Thai blood samples

BACKGROUND

Hepatitis C virus (HCV) infection is an important cause of liver cancer in Thailand. The highest prevalence of anti-HCV positive among Thai blood donors is found in the northeastern region. The present analysis of the genotype distribution among anti-HCV positive northeastern-Thai blood donors was conducted to provide a base for the epidemiological pattern of HCV infection in this region.

MATERIALS AND METHODS

A total of 112 HCV seropositive healthy blood donors were randomly selected and tested for the presence of HCV-RNA by RT-PCR. HCV-RNA positive samples were genotyped by direct sequencing at core region genomes and confirmed by phylogenetic analysis.

RESULTS

HCV viremia was found in 94.6% (106/112) of HCV seropositive blood donors. There were 3 major genotypes distributed among this population. HCV genotype 3a was the most prevalent (71.7%) followed by genotypes 1a (7.5%), 1b (7.5%), 6i (3.8%), 6f (2.8%) and 6n (1.9%).

CONCLUSIONS

HCV genotype 3a in asymptomatic infections in northeastern Thailand is significantly higher than other previous reports. Subgenotype 6 prevalence is less than in neighboring countries and distribution patterns differ. The findings are relevant as predictors for using interferon therapy in this population.

Genotypic distribution of hepatitis C virus in Thailand and Southeast Asia

The majority of hepatitis C virus (HCV) infection results in chronic infection, which can lead to liver cirrhosis and hepatocellular carcinoma. Global burden of hepatitis C virus (HCV) is estimated at 150 million individuals, or 3% of the world's population. The distribution of the seven major genotypes of HCV varies with geographical regions. Since Asia has a high incidence of HCV, we assessed the distribution of HCV genotypes in Thailand and Southeast Asia. From 588 HCV-positive samples obtained throughout Thailand, we characterized the HCV 5' untranslated region, Core, and NS5B regions by nested PCR. Nucleotide sequences obtained from both the Core and NS5B of these isolates were subjected to phylogenetic analysis, and genotypes were assigned using published reference genotypes. Results were compared to the epidemiological data of HCV genotypes identified within Southeast Asian. Among the HCV subtypes characterized in the Thai samples, subtype 3a was the most predominant (36.4%), followed by 1a (19.9%), 1b (12.6%), 3b (9.7%) and 2a (0.5%). While genotype 1 was prevalent throughout Thailand (27-36%), genotype 3 was more common in the south. Genotype 6 (20.9%) constituted subtype 6f (7.8%), 6n (7.7%), 6i (3.4%), 6j and 6m (0.7% each), 6c (0.3%), 6v and 6xa (0.2% each) and its prevalence was significantly lower in southern Thailand compared to the north and northeast (p = 0.027 and p = 0.030, respectively). Within Southeast Asia, high prevalence of genotype 6 occurred in northern countries such as Myanmar, Laos, and Vietnam, while genotype 3 was prevalent in Thailand and Malaysia. Island nations of Singapore, Indonesia and Philippines demonstrated prevalence of genotype 1. This study further provides regional HCV genotype information that may be useful in fostering sound public health policy and tracking future patterns of HCV spread.

Hepatitis C virus genotypes circulating in patients with chronic hepatitis C in Thailand and their responses to combined PEG-IFN and RBV therapy

Different genotypes of hepatitis C virus (HCV) are circulating in different areas of the world. In Thailand, distribution of HCV genotypes has been investigated mostly in the central area while the information in other regions is limited. This study aimed to determine the HCV genotypes circulating in chronic hepatitis C patients in Chiang Mai, Thailand and to investigate the response of different HCV genotypes to pegylated interferon (PEG-IFN) and ribavirin (RBV) treatment. Patients infected chronically with HCV were treated with PEG-IFN/RBV based on the standard regimens for each HCV genotype and followed up the patients until the end of treatment and 6 months afterward. Out of 158 patients, three major HCV genotypes and eight subtypes were identified. Genotype 3 was the most predominant at 54.5%, followed by genotypes 1 (31%) and 6 (14.5%). Among subtypes, 3a was the most prevalent subtype (45%), followed by 1b (18.4%), 1a and 6f (each at 12.6%), 3b (9.5%), and 6a, 6i, 6n (each at 0.63%). Patients with genotype 3 showed higher rate of responding to the treatment at 80.2% compared to genotypes 1 (73.5%) and 6f (65%). Additionally, patients with genotype 6f showed higher rate of relapsing (25%) compared to genotypes 1 and 3 (14.3% and 16.3%, respectively). In conclusion, this study reported multiple HCV genotypes circulated in Thai patients and the response of different HCV genotypes to PEG-IFN/RBV treatment.

Epidemiology and treatment of hepatitis C genotypes 5 and 6

Chronic hepatitis C infection is a major global health problem. The WHO estimates the number of infected people worldwide to be approximately 170 million. The estimated number of hepatitis C virus (HCV)-infected people in Canada is approximately 250,000, with approximately 5000 Canadians newly infected each year. Based on the identification of genomic differences, HCV has been classified into six genotypes; genotype may influence the outcome of antiviral therapy. HCV genotypes 1, 2 and 3 are widely distributed throughout the world and have been the focus of the majority of epidemiological, natural course and treatment studies. Although HCV genotypes 5 and 6 are prevalent in certain geographical areas, they are studied less extensively. HCV genotypes 5 and 6 are uncommon in Canada and account for less than 5% of HCV-infected Canadians. However, immigration and travel can alter the epidemiology of these uncommon genotypes. The present article reviews and summarizes the available data regarding the epidemiology and treatment of HCV genotypes 5 and 6. Genotype 5 is endemic in the northern part of South Africa while genotype 6 is reported primarily in Asia. Available data show that 48 weeks of treatment with a combination of pegylated interferon and ribavirin lead to a higher sustained virological response compared with HCV genotypes 1 and 4. None of the approved direct-acting antiviral agents is currently recommended for the treatment of HCV genotypes 5 or 6.

Resource Utilization and Direct Medical Costs of Chronic Hepatitis C in Thailand: A Heavy but Manageable Economic Burden

OBJECTIVE

To estimate the cost for the management of chronic hepatitis C (CHC) and related morbidities by using a payer perspective in Thailand.

METHODS

Data elements were extracted from medical records of 542 patients newly diagnosed with CHC in five tertiary care hospitals across Thailand. All patients were divided into five health states: noncirrhotic CHC, hepatitis C virus (HCV)-related compensated cirrhosis, HCV-related decompensated cirrhosis, HCV-related hepatocellular carcinoma, and HCV-related liver transplantation. Resource utilization data for each patient during a 12-month follow-up study period were compiled, and reference prices published by the Thai government were used to estimate the cost for each health state. The average cost was calculated and categorized into various groups, for example, laboratory and diagnostic tests, procedures, medication, and hospitalization.

RESULTS

The average number of outpatient visits per patient was approximately six visits in all cohorts. The HCV-related hepatocellular carcinoma and liver transplantation cohorts had a higher average number of inpatient admissions per patient. The average number of days per admission varied from fewer than 3 days to 1 week or more across all the health states. The average annual total cost per patient varied across all health states from approximately 170,000 to 600,000 baht, and medication cost was the largest portion in every cohort, except the HCV-related liver transplantation cohort in year 1. Among all medications, the average annual antiviral medication cost per patient was the largest portion in the noncirrhotic CHC and HCV-related compensated cirrhosis cohorts.

CONCLUSIONS

CHC was a costly disease in Thailand. The average annual medication cost was the largest portion in every health state, except HCV-related liver transplantation.

Systematic review: Asian patients with chronic hepatitis C infection

BACKGROUND

Chronic hepatitis C (CHC) infection is a risk factor for both the development of end-stage liver disease and hepatocellular carcinoma (HCC). Globally, approximately 170 million people are chronically infected with the hepatitis C virus (HCV), and the majority of these individuals come from the western Pacific and Southeast Asia regions (94.6 million persons combined). CHC is an understudied and underappreciated health problem in many Asian countries and in the US, where Asians represent one of the fastest growing groups of new Americans.

AIM

To perform a systematic review of the current literature on the epidemiology, diagnosis and screening, clinical characteristics and response to anti-viral therapy of Asians with CHC.

METHODS

Using a PubMed search of 'hepatitis C' and 'Asia,' 341 original manuscripts published in peer-reviewed journals were identified, and 99 were selected based on their relevance.

RESULTS

Many Asian CHC patients do not have easily identifiable risk factors and may be underdiagnosed. Rates of HCV infection in Asians on community screening in the US are unexpectedly high, and there is a high prevalence of HCV genotype 6 in Southeast Asia and Southern China. HCV-infected Asians tend to present at older age and may have higher risk of HCC; however, they respond better to anti-viral therapy than non-Asians across all HCV genotypes.

CONCLUSIONS

Given the high HCV endemicity in Asia, lack of identifiable risk factors and favourable treatment response rates in Asians, we advocate the screening for HCV infection of all Asians who come from areas where HCV prevalence is ≥2%.

Systematic review: epidemiology of hepatitis C genotype 6 and its management

BACKGROUND

Hepatitis C virus (HCV) genotype 6 is common among patients from Southeast Asia and the surrounding regions, where HCV prevalence is also high. HCV genotype 6 has great genetic diversity and different response to antiviral therapy compared with the more commonly known genotype 1.

AIM

Our goal was to provide a systematic review of the current literature on the epidemiology, classification and treatment of HCV genotype 6.

METHODS

A search using PubMed for 'hepatitis C' AND 'genotype 6' produced a total of 47 articles, of which 33 articles were found to be relevant and included in this review. Additional articles were identified using the reference lists of these 33 primary articles.

RESULTS

The prevalence of HCV genotype 6 is estimated to be as high as 50% in some regions of Southeast Asia with demonstrated significance among intravenous drug users and thalassemia major patients. Although previous line probe assays may have misclassified HCV genotype 6 as genotype 1, newer line probe assays can more accurately and reliably determine HCV genotype. Patients infected with HCV genotype 6 respond better to interferon-based therapy compared with those infected with genotype 1, although patient baseline clinical characteristics and side effect profiles are similar between HCV genotype 6 and other HCV genotypes.

CONCLUSIONS

Future studies should seek to clarify issues regarding early predictors for treatment response in patients with HCV genotype 6, and the impact of ethnic and genotypic factors to treatment response in HCV genotype 6 patients.

A systematic review of hepatitis C virus epidemiology in Asia, Australia and Egypt

BACKGROUND

The hepatitis C pandemic has been systematically studied and characterized in North America and Europe, but this important public health problem has not received equivalent attention in other regions.

AIM

The objective of this systematic review was to characterize hepatitis C virus (HCV) epidemiology in selected countries of Asia, Australia and Egypt, i.e. in a geographical area inhabited by over 40% of the global population.

METHODOLOGY

Data references were identified through indexed journals and non-indexed sources. In this work, 7770 articles were reviewed and 690 were selected based on their relevance.

RESULTS

We estimated that 49.3-64.0 million adults in Asia, Australia and Egypt are anti-HCV positive. China alone has more HCV infections than all of Europe or the Americas. While most countries had prevalence rates from 1 to 2% we documented several with relatively high prevalence rates, including Egypt (15%), Pakistan (4.7%) and Taiwan (4.4%). Nosocomial infection, blood transfusion (before screening) and injection drug use were identified as common risk factors in the region. Genotype 1 was common in Australia, China, Taiwan and other countries in North Asia, while genotype 6 was found in Vietnam and other Southeast Asian countries. In India and Pakistan genotype 3 was predominant, while genotype 4 was found in Middle Eastern countries such as Egypt, Saudi Arabia and Syria.

CONCLUSION

We recommend implementation of surveillance systems to guide effective public health policy that may lead to the eventual curtailment of the spread of this pandemic infection.

A shift in the hepatitis C virus genotype dominance in blood donor samples from Thailand

Hepatitis C virus (HCV) can be classified into six major genotypes. The HCV genotypes variability accounts for its geographical distribution, its responses to treatments and the clinical outcomes. The aim of this study was to determine the distribution of HCV genotypes among volunteer blood donors in Thailand. Samples from 135 anti-HCV positive blood donors were analyzed. HCV RNA and genotyping was carried out using nested polymerase chain reaction (PCR) and genotype-specific primer PCR for a portion of the core region. HCV RNA was detected in 109 samples (80.7%). Genotype analysis demonstrated four different genotypes. The most common was genotype 3a (36.7%), followed by genotype 6 (29.4%), 1a (19.3%), 1b (6.4%) and mixed infection (1.8%). Seven samples were untyped (6.4%) in the present study. In several previous reports, the prevalence found in Thailand was HCV genotypes 3, 1 and 6. The present results show an increasing importance of the genotype 6 in HCV infections. This study has also described for the first time in Thailand mixed infections of HCV genotypes.

Randomized controlled trial of pegylated interferon-alfa 2a and ribavirin in treatment-naive chronic hepatitis C genotype 6

Hepatitis C virus (HCV) genotype is an important criteria in determining duration of therapy and predictor of sustained virologic response (SVR) to pegylated interferon (PEG IFN) and ribavirin (RBV) therapy. Optimal duration of therapy for patients with HCV genotype 6 is not known. We conducted a multicenter, open-label randomized controlled trial of patients with HCV genotype 6 at five gastroenterology clinics in the western U.S. Patients were stratified by viral load and histologic stage and assigned to receive PEG IFN-α2a 180 μg subcutaneously weekly and weight-based oral RBV 800 to 1,200 mg daily for 24 or 48 weeks. Primary outcome measurement was SVR rate by intention-to-treat analysis. From February 2005 to October 2007 a total of 60 patients (age 51 ± 10 years, 47% male, log HCVRNA 6.3 ± 1.1 IU/mL) were enrolled: 27 patients to 24 weeks and 33 patients to 48 weeks of therapy. In the 24-week and 48-week groups, 96% and 97% achieved early virologic response (P = 0.90); 89% versus 94% achieved end of therapy virologic response (P = 0.48). SVR was achieved in 70% versus 79% of patients assigned to 24 weeks versus 48 weeks (P = 0.45). Rapid virologic response (RVR) was a significant predictor of SVR in the 48-week group and trending towards significance in the 24-week group: 82% and 83% of those with RVR achieved SVR versus 33% and 29% for the 24-week and 48-week groups, respectively (P = 0.07 and P = 0.02).

CONCLUSION

There was no significant difference in SVR rates in patients with HCV genotype 6 treated with PEG IFN-α2a and RBV for 24 versus 48 weeks.

Natural history of chronic hepatitis C: genotype 1 versus genotype 6

BACKGROUND & AIMS

Data on the natural history of chronic hepatitis C virus (HCV) genotype 6 is lacking.

METHODS

We compared the natural history of 138 HCV genotype 1 patients (median age: 50) with 78 HCV genotype 6 patients (median age: 46.5). Baseline demographic data including gender, route of transmission, liver biochemistry, HCV RNA levels, and serial alanine aminotransferase (ALT) levels were compared. The rate of development of complications and mortality were also analyzed.

RESULTS

A total of 71.7% and 8.7% of genotype 1 patients were infected through blood transfusion and intravenous drug addiction, respectively, compared with 56.4% and 28.2% for genotype 6 patients, respectively (p<0.05). There were no differences in the baseline liver biochemistry in terms of ALT, albumin, bilirubin, alpha-fetoprotein (AFP), and HCV RNA levels between the two groups. Comparison of the proportion of normal and abnormal ALT levels between the two groups showed no statistical difference (p=0.121). There was also no statistical difference in the cumulative rate of development of cirrhotic complications and hepatocellular carcinoma (p=0.358) and mortality (p=0.649) between the two groups.

CONCLUSIONS

HCV genotype 1 patients were largely infected through blood transfusion, while a statistically larger proportion of genotype 6 patients were infected through intravenous drug injection. Both genotypes have comparable liver biochemistry, HCV viral load, and similar rates of development of cirrhotic complications and mortality.

Geographic distribution of hepatitis C virus genotype 6 subtypes in Thailand

The nucleotide sequence of hepatitis C virus (HCV) genotype 6 found mostly in south China and south-east Asia, displays profound genetic diversity. The aim of this study to determine the genetic variability of HCV genotype 6 (HCV-6) in Thailand and locate the subtype distribution of genotype 6 in various geographic areas. Four hundred nineteen anti-HCV positive serum samples were collected from patients residing in - the central part of the country. HCV RNA positive samples based on reverse transcriptase- polymerase chain reaction (RT-PCR) of the 5'UTR were amplified with primers specific for the core and NS5B regions. Nucleotide sequences of both regions were analyzed for the genotype by phylogenetic analysis. To determine geographic distribution of HCV-6 subtypes, a search of the international database on subtype distribution in the respective countries was conducted. Among 375 HCV RNA positive samples, 71 had HCV-6 based on phylogenetic analysis of partial core and NS5B regions. The subtype distribution in order of predominance was 6f (56%), 6n (22%), 6i (11%), 6j (10%), and 6e (1%). Among the 13 countries with different subtypes of HCV-6, most sequences have been reported from Vietnam. Subtype 6f was found exclusively in Thailand where five distinct HCV-6 subtypes are circulating. HCV-6, which is endemic in south China and south-east Asia, displays profound genetic diversity and may have evolved over a considerable period of time.

Changes in modes of hepatitis C infection acquisition and genotypes in southwest China

BACKGROUND

The shift in the distribution of HCV genotypes could have a significant impact on practical medical issues.

OBJECTIVES

To describe the recent distribution and evolution of HCV genotypes in southwest China.

STUDY DESIGN

HCV genotypes were determined by nucleotide sequencing of the CE1 regions followed by phylogenic analysis with the published HCV genotype. HCV genotype distribution was analyzed according to patients' age, risk exposure, and the first time of risk exposure.

RESULTS

Among the 371 cases, subtypes 1a (0.8%), 1b (42.0%), 2a (9.7%), 3a (12.1%), 3b (21.0%), 4a (0.3%), and 6a (14.0%) were found. Genotypes 3 and 6 were significantly more frequent (85.4%) among IDUs than among other subjects (32.5%, P<0.001), they were also more frequent among subjects aged 40 years or under (63.6%) than older patients (21.6%, P<0.001), among patients infected after 1997 (54.4%) than those infected before 1997 (27.3%, P=0.001). Age 40 years or under (P<0.001) and infection via IDU (P<0.001) were independently associated with genotypes 3 and 6 in the multivariate stepwise logistic regression analysis. IDU was detected as a cause of infection in 27.8% of HCV cases; it was more frequent among younger patients (40.4%) than older ones (7.1%, P<0.001), among patients infected after 1997 (40.3%) than those infected before 1997 (16.2%, P<0.001).

CONCLUSION

In southwest China, the relative prevalence of genotypes 3 and 6 has increased significantly, and that of genotypes 1b and 2a has declined significantly among young patients. This shift in distribution was associated with changes in the modes of HCV acquisition.

Genetic history of hepatitis C virus in East Asia

The hepatitis C virus (HCV), which currently infects an estimated 3% of people worldwide, has been present in some human populations for several centuries, notably HCV genotypes 1 and 2 in West Africa and genotype 6 in Southeast Asia. Here we use newly developed methods of sequence analysis to conduct the first comprehensive investigation of the epidemic and evolutionary history of HCV in Asia. Our analysis includes new HCV core (n = 16) and NS5B (n = 14) gene sequences, obtained from serum samples of jaundiced patients from Laos. These exceptionally diverse isolates were analyzed in conjunction with all available reference strains using phylogenetic and Bayesian coalescent methods. We performed statistical tests of phylogeographic structure and applied a recently developed "relaxed molecular clock" approach to HCV for the first time, which indicated an unexpectedly high degree of rate variation. Our results reveal a >1,000-year-long development of genotype 6 in Asia, characterized by substantial phylogeographic structure and two distinct phases of epidemic history, before and during the 20th century. We conclude that HCV lineages representing preexisting and spatially restricted strains were involved in multiple, independent local epidemics during the 20th century. Our analysis explains the generation and maintenance of HCV diversity in Asia and could provide a template for further investigations of HCV spread in other regions.

The unique HCV genotype distribution and the discovery of a novel subtype 6u among IDUs co-infected with HIV-1 in Yunnan, China

The Yunnan province is the epicenter of HIV-1 epidemics in China and a center for drug trafficking to the other parts of the world. In six prefectures of this province, a total of 132 IDUs were recruited to determine the sero-prevalence of HCV and HIV-1 and the positive rates were 93.94% and 68.18%, respectively (P<0.001). Co-infection with HCV and HIV-1 was found among 89 IDUs, of whom several HCV fragments were amplified and sequenced. Sequences of the HCV 5'NCR-C and NS5B region were determined from 82 IDUs. Phylogenetic analyses showed consistent genotyping among 80 IDUs. Among them HCV genotypes 1a, 1b, 3a, 3b, 6a, 6n, and a tentatively assigned novel 6u subtype were found in 1 (1.25%), 16 (20%), 19 (23.75%), 24 (30%), 4 (5%), 9 (11.25%) and 7 (8.75%) individuals, respectively. In two IDUs, genotyping results were discordant, suggesting mixed HCV infections or recombination. The proportion of patients with HCV 1b tended to decrease from the north to south and from the east to west in this province. Genotype 3 and 6 strains were more frequent in the southern prefectures. The novel subtype 6u strains were only detected in Dehong which borders Myanmar. Our findings showed a unique pattern of HCV genotype distribution, which is similar to that in the southeastern Asian countries but distinct from that among the general population in China. Routes of drug trafficking and the resulting high prevalence of HIV-1 infection may have contributed to this pattern of HCV genotype distribution.

HIV and hepatitis C coinfection

The significant burden of HIV/hepatitis C virus (HCV) coinfection is increasingly recognized worldwide, and in particular within the Asia-Pacific region. Individuals who are coinfected with both viruses are at risk from accelerated liver disease and consequently cirrhosis, liver failure, and hepatocellular carcinoma. In addition, coinfected individuals may have altered immunological responses to HAART and are at increased risk of highly active antiretroviral therapy (HAART)-related hepatotoxicity. Treatment for HCV infection in HIV-infected individuals is with standard pegylated interferon and ribavirin therapy, and all HIV/HCV coinfected subjects should undergo suitability for HCV treatment assessment. Response rates to HCV therapy are generally 10-15% lower than in HCV monoinfection, and therapy may be complicated by issues of drug interactions and significant toxicity. However, greater understanding of baseline factors can contribute to better prediction of treatment outcome, and monitoring of on-treatment virological responses increasingly allows individualization of therapy. Where possible, treatment of HCV is often advisable before HAART is required to avoid the issues of drug interactions on HCV therapy and the risk of HAART-related hepatotoxicity. Early diagnosis of both HIV and HCV infection is essential to most effectively manage HIV-HCV-coinfected individuals. New therapies, including HCV protease and polymerase inhibitors, are in development and may widen therapeutic options for HIV-HCV-coinfected individuals into the future.

Hepatitis C virus genotype distribution in Myanmar: Predominance of genotype 6 and existence of new genotype 6 subtype

AIM

This study was performed to determine the prevalence and distribution of hepatitis C virus (HCV) genotypes in Myanmar.

METHODS

A total of 1333 peripheral blood samples were collected from four different border cities of Myanmar. The anti-HCV antibody-positive serum samples were identified. HCV was genotyped by reverse transcriptase polymerase chain reaction, direct DNA sequencing and phylogenetic analysis on the partial core genome.

RESULTS

The overall prevalence of HCV infection was 11.6% (154/1333). Regionally, it was 13.5% (47/349) in the north-eastern city, 12.8% (64/501) in the north-western city, 4.2% (16/380) in the southern city and 26.2% (27/103) in the western city. HCV was genotyped in 145/154 (94.2%) samples. Genotype 6 was the most prevalent genotype in this study (71/145, 49%), followed by genotype 3 (57/145, 39.3%), genotype 1 (16/145, 11%), and genotype 2 (1/145, 0.7%). Genotype 6 was mostly found in the northern cities and genotype 3 in the southern and western cities of Myanmar. Multiple HCV genotypes/subtypes were successfully characterized as 1a, 1b, 2a, 3a, 3b, 6m, 6n, and a new 6 subtype. Among them, subtype 6n was the most predominant subtype (38.6%), followed by subtype 3b (29.7%), 3a (9.6%), 6m (9%), 1b (6.9%), 1a (4.1%), new 6 subtype (1.4%) and 2a (0.7%). Subtype 6n was more widely distributed in the northern cities whereas subtype 3b was more common in the western city. The newly discovered genotype 6 subtype was from the northern cities.

CONCLUSIONS

The results indicate there are regional differences of HCV genotype distribution in Myanmar. There is a distinct geographic variation from other South-East Asian countries in terms of the existence of the new genotype 6 subtype.

Hepatitis C virus (HCV) core antigen assay to detect ongoing HCV infection in thai injection drug users

We evaluated a quantitative enzyme immunoassay (trak-C) for hepatitis C virus core antigen (HCV core Ag) by testing serum specimens from 820 injection drug users in Thailand with anti-HCV antibodies. The HCV genotypes in this population include genotypes 3 and 6, which have not been extensively tested with this assay. Among these specimens, 629 (76.7%) yielded positive results, with HCV core Ag concentrations predominantly spanning (35.7%) or above (58.2%) the measurable range of 1.5 to 100 pg/ml. To assess reproducibility, we retested 30 specimens representing six core Ag ranges; the mean coefficient of variation for each range was < or = 9.7% (highest for 1.5 to 25 pg/ml). We also tested 204 specimens of the 820-specimen set for HCV RNA: while 146 (71.6%) were core Ag positive, 168 (82.4%) had detectable HCV RNA, of which 96% were typeable as genotype 3 (39%), 1 (31%), or 6 (26%) by nested reverse transcription-PCR. Among RNA-positive specimens, 86.9% had core Ag; 94% of the RNA negatives were core Ag negative. While there was no apparent bias for detecting core Ag representing the tested genotypes, median quantified results were higher for types 1a and 6 than for genotype 3 (P = 0.01); similarly, the median core Ag concentration was higher in HCV-human immunodeficiency virus-coinfected subjects than in HCV-monoinfected subjects. Our results demonstrated a good correlation between core Ag and HCV RNA in this population with high frequencies of genotypes 3 and 6. Because most core Ag concentrations were greater than those in the measurable range, we recommend a 10-fold dilution of the specimen before quantification. Reproducibility, low technical requirements, and high throughput should make this assay useful for clinical or research monitoring of HCV levels during active infection.

Molecular epidemiology of hepatitis B and C virus infections in Asia

The present paper provides a review of the current literature regarding the molecular-based epidemiology of hepatitis B virus (HBV) and hepatitis C virus (HCV), which are very important viruses underlying the etiology of blood-borne infectious diseases worldwide. Particularly, both HBV and HCV are widespread on the Asian continent and are associated with acute and chronic liver diseases, including hepatocellular carcinoma. HBV has been classified into genotypes A through G and shown to have a distinct geographic distribution. In Asia, genotypes B and C of HBV prevail, and genotype C has been shown to cause more serious liver disease than genotype B. High prevalence of HBV mutants with various forms, such as the pre-S mutant, basal core promoter mutant, YMDD motif mutant and vaccine escape mutant, were seen in Asia and these were found to be related to the severity of liver disease and sensitivity to therapy. HCV has also been classified into multiple genotypes and associated with geographic distribution. HCV genotype 1 is less sensitive to interferon therapy and may be associated with the presence of more serious liver disease than the other genotypes. Data on the relation among the HBV/HCV genotypes, their pathogenicity in chronic liver diseases including hepatocellular carcinoma and their effect on therapy are awaited with great interest, especially in Asia, which is an endemic region of blood-borne hepatitis viruses.

Infection with hepatitis C virus among intravenous-drug users: prevalence, genotypes and risk-factor-associated behaviour patterns in Thailand

Hepatitis C virus (HCV) infection, a major problem worldwide, is usually transmitted parenterally or by use of contaminated needles among intravenous-drug users (IVDU). In a cross-sectional study, demographic data were collected and behaviour patterns investigated in interviews with 453, consenting IVDU. Blood samples were collected from each interviewee and checked for anti-HCV antibodies and, in a PCR-based assay, for the RNA of HCV. Almost all (92.5%) of the IVDU investigated were found positive for anti-HCV and/or the viral RNA. Most (73.5%) of those positive for HCV RNA were found to be infected with genotype 3a alone, the rest being infected with 1b (17.9%), 6a (3.5%), 3b (1.4%), 1a (1.0%), or both 3a and 6a (2.1%) or having non-typable infections (0.6%). Curiously, 26.0% of those who appeared seronegative for anti-HCV were positive for HCV RNA. The longer an interviewee had been using intravenous drugs, the more likely he or she was to be infected with HCV. Among the IVDU, the sharing of needles, syringes and/or other drug-related paraphernalia appeared to be the behaviour carrying the highest risk of HCV infection, giving an adjusted odds ratio and (95% confidence interval) of 4.84 (1.88-12.43). Programmes of needle and syringe exchange should probably be implemented among IVDU in Thailand and elsewhere, to slow the transmission of HCV.

Genotype and viral load as prognostic indicators in the treatment of hepatitis C

Interferon-alpha (IFN-alpha), either alone or in combination with ribavirin, is the standard treatment for patients with hepatitis C. However, most patients do not achieve a sustained remission with this treatment regimen. A number of studies have demonstrated that genotype, baseline viral load and/or a decrease in viral load early after treatment induction are the major predictive factors for response to treatment with IFN. Patients with hepatitis C virus (HCV) genotype 1 are more resistant to treatment with IFN, whereas low viral load at baseline and a marked decline in the HCV RNA level during the first 2-12 weeks of IFN therapy are associated with enhanced treatment efficacy. These variables could potentially be used to develop treatment algorithms that tailor therapies for specific clinical situations. Continued development and refinement of such algorithms would facilitate both the selection of patients who are most likely to benefit from therapy and the development of optimal treatment regimens for different patient groups. Predictive factors will also enable clinicians to identify subsets of patients who are not expected to respond well to current treatment. The development of new delivery methods for IFN that produce sustained antiviral pressure may provide a means of treating these previously difficult-to-treat patient groups.

Chronic hepatitis C in Sweden: genotype distribution over time in different epidemiological settings

Hepatitis C virus (HCV) strains are divided into 6 genotypes and several subtypes. Recent studies reported a change in the relative frequency of genotypes within certain regions. We studied the HCV genotype in 312 Swedish patients with chronic hepatitis C, using a core region primer-specific PCR, and grouped the patients according to parenteral risk factors. The date of infection could be estimated in 127 cases. Genotypes 1a (35%) and 3 (31%) were the most common genotypes, followed by genotype 2 (17%), while only 6% had genotype 1b. Genotype 3 was relatively more frequent among subjects infected sexually or by intravenous drug use. The genotype distribution was different from that in studies from other parts of the world, with a lower frequency of genotype 1 (especially 1b) and a higher frequency of genotype 3. The frequency of genotype 1b has decreased and genotype 3 increased over time. The reasons for a different distribution of genotypes in Sweden, compared with other countries, might be a relatively recent introduction of HCV into the population, or a different pattern of transmission.

A serotyping assay for hepatitis C virus in Southeast Asia

A serotyping assay for hepatitis C virus (HCV) was evaluated with samples from Thailand, where the distribution of HCV genotypes was different from that in Western countries where the assay was designed and validated. The sensitivity of the assay was low (58%) for HCV RNA-positive samples compared to that of the genotyping assay (95%, P < 0.01). In addition, only 36% of anti-HCV-positive but HCV RNA-negative samples could be serotyped. The serotypes and genotypes were identical in 96% of the samples that could be typed by both methods. Most of the samples with genotype 6, which was common in Southeast Asia, were nontypeable by this serotyping assay.