Evidence for high genetic diversity and long-term endemicity of hepatitis C virus genotypes 1 and 2 in West Africa

Hepatitis C virus infection in Guinea-Bissau: a sexually transmitted genotype 2 with parenteral amplification?

Background

Sub-Saharan Africa is the continent with the highest prevalence of Hepatitis C virus (HCV) infection. Genotype 2 HCV is thought to have originated from West Africa several hundred years ago. Mechanisms of transmission remain poorly understood.

Methodology/Principal Findings

To delineate mechanisms for HCV transmission in West Africa, we conducted a cross-sectional survey of individuals aged ≥50 years in Bissau, Guinea-Bissau. Dried blood spots were obtained for HCV serology and PCR amplification. Prevalence of HCV was 4.4% (47/1066) among women and 5.0% (27/544) among men. In multivariate analysis, the independent risk factors for HCV infection were age (baseline: 50–59 y; 60–69 y, adjusted odds ratio [AOR]: 1.67, 95% CI: 0.91–3.06; ≥70 y, AOR: 3.47, 95% CI: 1.89–6.39), belonging to the Papel, Mancanha, Balanta or Mandjako ethnic groups (AOR: 2.45, 95% CI:1.32–4.53), originating from the Biombo, Cacheu or Oio regions north of Bissau (AOR: 4.16, 95% CI: 1.18–14.73) and having bought or sold sexual services (AOR: 3.60, 95% CI: 1.88–6.89). Of 57 isolates that could be genotyped, 56 were genotype 2.

Conclusions

Our results suggest that transmission of HCV genotype 2 in West Africa occurs through sexual intercourse. In specific locations and subpopulations, medical interventions may have amplified transmission parenterally.

Hepatitis C virus infection and genotypes in Antananarivo, Madagascar

The prevalence of hepatitis C virus (HCV) genotypes in Madagascar is not well known. Serum samples were obtained from 2,169 individuals selected by random sampling in the population living in Antananarivo city. Using HCV antibody test (Monolisa anti-HCV Plus version 2), 36 (1.7%) of the 2,169 samples were positive. The presence of HCV RNA was determined by using reverse transcription polymerase chain reaction amplifying the 5'-untranslated region (UTR): HCV RNA was detected in 17 of the 36 HCV antibodies positive samples. The genotype was determined using BLAST tool with another 5'-UTR fragment. The phylogenetic analysis of the polymerase (NS5b) and envelope (E1/E2) fragment sequences showed a low level of diversity compared to the high diversity in other African countries: subtype 1b (nine cases, 52.9%) and genotype 2 (eight cases, 47.1%) including subtype 2b (six cases), subtype 2k (one case), and one unclassified subtype. BLAST search with the 5'-UTR fragment sequence of this unclassified subtype identified that strain as subtype 2a.

The economics of hepatitis C virus

Hepatitis C virus is a disease of major public health significance throughout the world in terms of overall morbidity and mortality and in its economic consequences and demands on medical resources. The global economic burden of this disease has yet to be fully realized. In this article the authors discuss the economic burden of hepatitis C, the economics of therapy, and the economics of its prevention and screening.

Molecular epidemiology of hepatitis C virus subtype 3a in injecting drug users

Hepatitis C virus subtype 3a (HCV-3a) originates from Asia and has spread widely among injecting drug users as well as other patient groups in industrialized countries. HCV subtype 3a infection remains highly prevalent and frequently transmitted in the population of intravenous drug users. The objective of this study was to understand better the mechanisms of the worldwide HCV-3a epidemics in drug users. Ninety-three sera from HCV-3a-infected IDUs from France, the United States, Brazil, Argentina, and Australia were studied. Phylogenetic analyses of the non-structural 5B region showed no specific clustering according to the continent of the patient's origin. Non-exclusive clusters of viral sequences from South America, Australia, and California were observed, but topologies were not supported by strong bootstrap values. The results suggest that HCV-3a has been transmitted from a common origin through a unique worldwide epidemic that rapidly spread among drug users. Regional transmission occurred in the recent past, leading to an embryonic genetic diversification of HCV-3a among local injecting drug user population.

Seroprevalence of six different viruses among pregnant women and blood donors in rural and urban Burkina Faso: A comparative analysis

A seroprevalence study was carried out of six different human pathogenic viruses, namely human immunodeficiency virus (HIV), hepatitis B virus (HBV), hepatitis C virus (HCV), human T-cell leukemia virus (HTLV), human herpesvirus type 8 (HHV-8), and dengue virus among pregnant women and blood donors from rural (Nouna) and urban (Ouagadougou) Burkina Faso, West Africa. A total of 683 samples from blood donors (n = 191) and pregnant women (n = 492) were collected from both sites and screened for the different virus infection markers resulting in the following prevalence values for Nouna or Ouagadougou, respectively: HIV 3.6/4.6, anti-HBV core (anti-HBc) 69.6/76.4, HBV surface antigen (HBsAg)14.3/17.3, HCV 2.2/1.5, HTLV 1.4/0.5, HHV-8 11.5/13.5, dengue virus 26.3/36.5. Individuals aged > or =25 years were more likely to be infected with HIV than those below 24 years (P < 0.05). Infection with HIV increased the likelihood of co-infection with other viruses, such as HHV-8, HBV and HTLV. Co-infection studies involving five viruses (HBV-HBsAg, HHV-8, HIV, HCV, and HTLV) showed that 4.8% (33/683) of the studied population were dually infected, with HBsAg+ HHV-8 (13/33), HBsAg+HIV (8/33) and HIV+HHV-8 (8/33) being the most common co-infections. Of the population studied 0.6% (4/683) was triply infected, the most common infection being with HBV+HIV+HHV-8 (3/4). There was no difference in the prevalence of HIV, anti-HBc, HBsAg, HCV, HTLV, and HHV-8 either among blood donors or pregnant women in urban or rural setting, while dengue virus prevalence was relatively lower in rural (26.3%) than in urban (36.5%) Burkina Faso.

A new subtype of hepatitis C virus genotype 1: complete genome and phylogenetic relationships of an Equatorial Guinea isolate

Hepatitis C virus (HCV) is the leading cause of chronic liver disease and is associated with hepatocellular carcinoma. However, there have been few studies on the distribution and genetic diversity of HCV isolates in non-developed countries. Here, the complete genome sequence of an HCV genotype 1 isolate from Equatorial Guinea is reported, the first complete HCV-1 genome of African origin. Phylogenetic analysis revealed that this sequence always grouped with sequences of genotype 1, but did not group clearly with any subtype described so far. An analysis of partial NS5B gene sequences with additional sequences of African origin also failed to find close similarities between the new sequence and any previously known isolate. Genetic divergence of the coding region of this new sequence with respect to the recognized subtypes of HCV-1 ranged from 20 to 22%. It is proposed that this isolate is a representative of a new, distinct variant of HCV subtype 1.

Genetic diversity and evolution of hepatitis C virus in the Latin American region

Hepatitis C virus (HCV) has been the subject of intense research and clinical investigations, as a consequence of the recognition of its major role in human disease. HCV evolution is a highly dynamic process. HCV exploits all known mechanisms of genetic variation, such as recombination and mutation, to ensure its survival. Like most RNA viruses, HCV circulates in vivo as a complex population of different but closely related variants, commonly referred to as a quasi species. This work describes the genetic variability of HCV in Latin America, with special emphasis on its diversification and recombination in this area of the world, and discusses how our knowledge of these issues can contribute to its control.

Genetic diversity of HCV genotype 2 strains in South Western France

Hepatitis C virus (HCV) is a major cause of chronic hepatitis and liver disease worldwide. The genetic heterogeneity of HCV and its spread among infected patients can be examined accurately by nucleotide sequencing. The diversity of HCV genotype 2 strains (HCV-2) was studied in a large cohort of patients in the Midi Pyrénées area of southern France. Phylogenetic analysis was performed on 344 NS5B sequences from patients infected with HCV-2. These included 145 strains whose E2 region was also analyzed, and epidemiological data were collected for the corresponding patients. HCV-2 accounts for 11.3% of HCV infections in this area. Phylogenetic analysis of NS5B sequences revealed eight subtypes, while that of the E2 region provided congruent results for 100% of strains. The most frequent subtypes were 2i (24.7%), 2k (22.4%) 2c (17.4%), and 2a (10.8%). The mean age of HCV-2-infected patients was 55.5 years. Epidemiological data showed that blood transfusion is the major route of infection, but it was not associated with any particular subtype. By contrast, intravenous drug users were infected predominantly with genotype 2a. HCV-2a-infected patients were younger than patients infected with other subtypes (48 vs. 56.5 years, P < 0.01). This study shows substantial genetic diversity of HCV-2 subtypes in the south of France and the spread of 2a strains via intravenous drug users.

Follow-up of the prevalence of hepatitis C virus genotypes in Spain during a nine-year period (1996-2004)

BACKGROUND

Recent data suggest that the prevalence of genotype 4 HCV strains among Spanish carriers is increasing.

OBJECTIVE

To assess changes in the prevalence of HCV genotypes in Spain during the last nine years.

METHODS

HCV RNA was amplified by the polymerase chain reaction from 3161 serum samples from unselected, anti-HCV-positive individuals, and the HCV genotype was identified by a reverse hybridisation assay (line probe assay, LiPA). Samples came from 17 different regions of Spain and were obtained between January, 1996 and December, 2004.

RESULTS

The overall prevalence of HCV genotypes was: 1b, 41.3%; 1a, 24.1%; 3, 19.6%; 4, 11.6%; 2, 3.1%; and 5, 0.3%. The prevalence of genotypes 1a, 3 and 4 increased significantly among patients born after 1950, and that of genotype 1b decreased among them. These significant differences in regard to age were also observed among patients lacking notified high-risk factors. A main switch-up in prevalence of genotypes 1a and 3 was found when patients born in 1941-1950 were compared with those born in 1951-1960, but the same finding in genotype 4 was delayed to patients born in 1961-1970.

CONCLUSIONS

Two separate epidemics of HCV seem to have occurred in Spain during the last 30 years. The former one involved the spread of HCV genotypes 1a and 3. The second was more recent, and involved the spread of genotype 4.

Consensus proposals for a unified system of nomenclature of hepatitis C virus genotypes

International standardization and coordination of the nomenclature of variants of hepatitis C virus (HCV) is increasingly needed as more is discovered about the scale of HCV-related liver disease and important biological and antigenic differences that exist between variants. A group of scientists expert in the field of HCV genetic variability, and those involved in development of HCV sequence databases, the Hepatitis Virus Database (Japan), euHCVdb (France), and Los Alamos (United States), met to re-examine the status of HCV genotype nomenclature, resolve conflicting genotype or subtype names among described variants of HCV, and draw up revised criteria for the assignment of new genotypes as they are discovered in the future. A comprehensive listing of all currently classified variants of HCV incorporates a number of agreed genotype and subtype name re-assignments to create consistency in nomenclature. The paper also contains consensus proposals for the classification of new variants into genotypes and subtypes, which recognizes and incorporates new knowledge of HCV genetic diversity and epidemiology. A proposal was made that HCV variants be classified into 6 genotypes (representing the 6 genetic groups defined by phylogenetic analysis). Subtype name assignment will be either confirmed or provisional, depending on the availability of complete or partial nucleotide sequence data, or remain unassigned where fewer than 3 examples of a new subtype have been described. In conclusion, these proposals provide the framework by which the HCV databases store and provide access to data on HCV, which will internationally coordinate the assignment of new genotypes and subtypes in the future.

A refined long RT-PCR technique to amplify complete viral RNA genome sequences from clinical samples: application to a novel hepatitis C virus variant of genotype 6

The goal of this study was to adapt a long RT-PCR technique to amplify large PCR fragments from the genome of hepatitis C virus (HCV) isolates using clinical samples. This was done by using a reverse transcriptase devoid of RNase H activity and a mixture of two antibody-bound thermostable polymerases to combine the high processivity of Taq and the high fidelity of Pwo with its 3'-->5' exonuclease activity. Other modifications included gentle handling during RNA extraction, the absence of tRNA and random primers, a two-step reverse transcription procedure to optimize cDNA synthesis, and increasing the annealing temperature for primers. With this approach, the HCV-1 genome (nucleotides 35-9282) was amplified consistently as two overlapping fragments of 5344 and 4675 bp from a pooled chimpanzee plasma sample containing approximately 10(6) genome copies of HCV RNA/ml. Using the conditions that we identified, 96% of the complete genomic sequence of a distinct HCV genotype 6 variant (km45) was determined from less than 300 microl of serum. This method should prove useful for molecular, epidemiological and clinical studies of hepatitis C where samples are limited but complete virus sequence is required, for example, identifying mutational hot spots of HCV under specific clinical conditions.

Genotype distribution and molecular epidemiology of hepatitis C virus in blood donors from southeast France

The genotype distribution of hepatitis C virus (HCV) in blood donors from southeast France was tracked for a period of 13 years (1991 to 2003). Virus genomes from 321 samples were analyzed by amplification and sequencing of the NS5b and E1 regions. The most frequent genotypes were 1b (30.2%), 1a (27.7%), and 3a (22.4%). Although it was less common, genotype 2 was characterized by the presence of strains belonging to 11 different subtypes, including 5 that had never been characterized. Genotypes 1a, 1b, 3a, and 4a presented typical "epidemic" profiles, with a large number of isolates per subtype and short mean genetic distances between isolates. Type 2 isolates displayed a typical "endemic" profile, with a large number of subtypes and very few isolates in each subtype. The epidemiology of HCV infection in southeast France changed radically during the study period in relation to modifications in the etiology of infection. We observed the emergence of new epidemic subtypes (subtypes 1a and 3) linked to intravenous drug use and a decrease in the types linked to blood transfusion and nosocomial infection (epidemic subtype 1b and endemic type 2). Comparison of strains from blood donors with strains from a cohort of inpatients in the same region during 2001 and 2002 demonstrated for the first time that the monitoring of blood donors is a generally valid indicator of HCV epidemiology in terms of genotype distribution.

The hepatitis C virus epidemic among injecting drug users

Given the economic and health costs of hepatitis C virus (HCV) infection, and the ongoing transmission within the injecting drug user (IDU) population, there is a need for improved understanding of HCV epidemiology within this risk group. We employed a recently developed method based on phylogenetic analysis to infer HCV epidemic history and to provide the first estimates of the rate of spread of subtypes 1a and 3a circulating within injecting drug user populations. The data indicates that HCV subtype 1a entered the IDU population on at least three separate occasions. Both subtypes demonstrate exponential population growth during the 20th century, with a doubling time of 7-8 years. The results provide a baseline for prediction of the future course of the HCV epidemic, and its likely response to transmission control policies.

HBV and HCV prevalence and viraemia in HIV-positive and HIV-negative pregnant women in Abidjan, Côte d'Ivoire: the ANRS 1236 study

A retrospective survey estimating the prevalence of hepatitis viruses B (HBV) and C (HCV) was conducted on samples taken in 1,002 African pregnant women (501 diagnosed as HIV-1 positive and 501 HIV-1 negative) participating in a clinical trial program conducted in Abidjan, Côte d'Ivoire (West Africa). Hepatitis B markers studied were HBs antigen (HBsAg), and if positive, HBe antigen/anti-HBe antibodies and HBV DNA. Two third generation (G3) HCV enzyme immunoassays (EIAs) were used for primary HCV screening. All anti-HCV antibody-positive sera were assessed further with supplementary assays (one another G3 EIA, RIBA 3.0, and HCV RNA). HCV genotypes were also determined. HBsAg was found in a similar proportion among HIV-positive (45/499, 9.0%, 95% confidence interval [95% CI], 6.6-11.9) and HIV-negative (40/498, 8.0%, 95% CI, 5.8-10.8) women (P = 0.58). The diagnosis of chronic hepatitis B, based on HBV DNA positive results, was more frequent in HIV-positive women (26.7%), compared to HIV-negative women (9.4%) (P = 0.06). In the case of hepatitis C infection, after supplementary testing allowing the elimination of frequent false-positive screening results, a prevalence rate of about 1% was found, both in HIV-positive (6/501, 1.2%, 95% CI, 0.44-2.59) and HIV-negative (4/501, 0.8%, 95% CI, 0.22-2.03) women (P = 0.53). Of the 10 samples confirmed positive and assessed for HCV RNA, eight (80%) were viraemic and belonged to HCV genotypes 1 or 2. The relative high frequency of HIV/HBV coinfection in Côte d'Ivoire emphasises the need for monitoring the risk of hepatotoxicity by antiretroviral therapy in such patients. We propose an accurate and cost-efficient algorithm for HCV diagnosis in Africa.

HCV and HIV co-infection in pregnant women attending St. Camille Medical Centre in Ouagadougou (Burkina Faso)

Five hundred and forty-seven pregnant women with less than 32 weeks of amenorrhoea, attending an antenatal clinic of St. Camille Medical Centre (SCMC) of Ouagadougou were enrolled for a hepatitis C virus (HCV) and HIV co-infection study. Fifty-eight (10.6%) were HIV positive and 18 (3.3%) were anti-HCV positive. Only seven pregnant women (i.e., 1.3%) had a documented HIV and HCV co-infection. HCV-RNA was found in 5 out of 18 (27.8%) patients, who had anti-HCV antibodies. The genotype analysis of these five patients showed that two were of 1b whereas three were of 2a genotype. Mother-to-infant transmission of the same HCV genotype (2a) was documented in only one case. High 1b prevalence has been reported in other parts of Africa, while 2a is the prevalent genotype (60%) in Burkina Faso. This genotype has a higher response rate to treatment. Serum transaminases were normal, also in presence of HCV-RNA. The higher than expected rate of co-infection in Burkina Faso seems to demonstrate a correlation between these two infections, which could influence the evolution of HIV and HCV diseases.

Genetic diversity and evolution of hepatitis C virus--15 years on

In the 15 years since the discovery of hepatitis C virus (HCV), much has been learned about its role as a major causative agent of human liver disease and its ability to persist in the face of host-cell defences and the immune system. This review describes what is known about the diversity of HCV, the current classification of HCV genotypes within the family Flaviviridae and how this genetic diversity contributes to its pathogenesis. On one hand, diversification of HCV has been constrained by its intimate adaptation to its host. Despite the >30 % nucleotide sequence divergence between genotypes, HCV variants nevertheless remain remarkably similar in their transmission dynamics, persistence and disease development. Nowhere is this more evident than in the evolutionary conservation of numerous evasion methods to counteract the cell's innate antiviral defence pathways; this series of highly complex virus-host interactions may represent key components in establishing its 'ecological niche' in the human liver. On the other hand, the mutability and large population size of HCV enables it to respond very rapidly to new selection pressures, manifested by immune-driven changes in T- and B-cell epitopes that are encountered on transmission between individuals with different antigen-recognition repertoires. If human immunodeficiency virus type 1 is a precedent, future therapies that target virus protease or polymerase enzymes may also select very rapidly for antiviral-resistant mutants. These contrasting aspects of conservatism and adaptability provide a fascinating paradigm in which to explore the complex selection pressures that underlie the evolution of HCV and other persistent viruses.

Hepatitis C virus (HCV) genotypes in the Caribbean island of Martinique: evidence for a large radiation of HCV-2 and for a recent introduction from Europe of HCV-4

Molecular epidemiological studies of hepatitis C virus (HCV) in the Caribbean may help to specify the origin and spread of HCV infection. Indeed, the Caribbean population is intermixed from European and African origins and geographically close to the American continent. We characterized HCV genotypes in the Caribbean island of Martinique. HCV genotypes were analyzed by sequencing or reverse hybridization in the 5' noncoding region (5'NC) in 250 HCV-monoinfected and 85 HCV-human immunodeficiency virus (HIV)-coinfected patients. In addition, sequencing in the nonstructural 5B (NS5B) gene was required to determine the subtype or to perform phylogenetic analysis in selected samples. Genotypes 1 to 6 were found, respectively, in 84.4, 6.8, 5.2, 2.8, 0.4, and 0.4% of 250 HCV-monoinfected patients and in 71.7, 7.1, 15.3, 5.9, 0, and 0% of 85 HCV-HIV-coinfected patients. HCV-1b was found in 66.4% of the HCV-monoinfected patients and was associated with blood transfusion, whereas HCV-1a was detected in 41.2% of the HCV-HIV-coinfected patients and was associated with intravenous drug use (IVDU). The HCV-3 strains belonged to subtype 3a and were linked to IVDU. Phylogenetic analyses were focused on HCV-2 and HCV-4, which are common in Africa. Two opposite patterns were evidenced. NS5B sequences from 19 HCV-2 isolates were affiliated with many different subtypes described either in Europe or in West Africa, suggesting an ancient radiation. In contrast, seven of the nine HCV-4 NS5B sequences ranged within HCV-4a and HCV-4d clusters spreading in continental France by the IVDU route. Epidemiological data demonstrate the recent introduction of HCV-4a and -4d subtypes into the Caribbean.

Phylogenetic analysis of hepatitis C virus isolates indicates a unique pattern of endemic infection in Cameroon

Hepatitis C virus (HCV) is a blood-borne pathogen that poses a significant threat to public health worldwide. The genetic diversity and distribution of HCV genotypes in non-Western countries, particularly subSaharan Africa, is poorly documented. This study reports a phylogenetic analysis of core and NS5B gene sequences of 37 HCV strains sampled in Cameroon. A high level of genetic diversity of both genotypes 1 and 4 was found, indicating a unique pattern of long-term HCV infection that has not been observed elsewhere. These results lead to the hypothesis that these HCV genotypes originated and diversified in west Central Africa before spreading to other regions.

Frequent recovery and broad genotype 2 diversity characterize hepatitis C virus infection in Ghana, West Africa

Hepatitis C virus (HCV) infection is thought to mostly become chronic and rarely resolves. HCV infection was serologically screened in 4,984 samples from Ghanaian blood donors, and 1.3% prevalence was found. At least 53% of confirmed anti-HCV carriers had no detectable viral RNA and were considered to have cleared the virus and recovered from the infection. Confirmation was authenticated by the presence of antibodies specific to at least two viral antigens, mostly NS3 and E2. Reactivity to HCV core antigens was lower in Ghanaian than United Kingdom blood donors. The minority of chronically infected donors carried a viral load significantly lower than an unselected comparative group of United Kingdom blood donors (2.5 x 10(5) versus 2.9 x 10(6) IU/ml; P = 0.004). HCV genotype 2 was largely predominant (87%). Sequence clustering was similarly broad in the E1/E2 and NS5 regions. The phylogenetic diversity and the incapacity to distinguish subtypes within genotype 2 in our and others' West African strains suggested that West Africa may be the origin of HCV genotype 2. The genetic diversity extended to the identification of strains clearly separated from known subtypes of genotype 2 and genotype 1. One strain appears to be part of a new HCV genotype. HCV infection in Ghana is characterized by a high rate of recovery and the predominance of broadly divergent genotype 2 strains.

Hepatitis C virus infection in a Brazilian population with sickle-cell anemia

Patients with sickle-cell anemia submitted to frequent blood transfusions are at risk of contamination with hepatitis C virus (HCV). Determination of HCV RNA and genotype characterization are parameters that are relevant for the treatment of the viral infection. The objective of the present study was to determine the frequency of HCV infection and the positivity for HCV RNA and to identify the HCV genotype in patients with sickle-cell anemia with a history of blood transfusion who had been treated at the Hospital of the HEMOPE Foundation. Sera from 291 patients were tested for anti-HCV antibodies by ELISA 3.0 and RIBA 3.0 Chiron and for the presence of HCV RNA by RT-PCR. HCV genotyping was performed in 19 serum samples. Forty-one of 291 patients (14.1%) were anti-HCV positive by ELISA and RIBA. Both univariate and multivariate analysis showed a greater risk of anti-HCV positivity in those who had started a transfusion regime before 1992 and received more than 10 units of blood. Thirty-four of the anti-HCV-positive patients (34/41, 82.9%) were also HCV RNA positive. Univariate analysis, used to compare HCV RNA-negative and -positive patients, did not indicate a higher risk of HCV RNA positivity for any of the variables evaluated. The genotypes identified were 1b (63%), 1a (21%) and 3a (16%). A high prevalence of HCV infection was observed in our patients with sickle-cell anemia (14.1%) compared to the population in general (3%). In the literature, the frequency of HCV infection in sickle-cell anemia ranges from 2 to 30%. The serological screening for anti-HCV at blood banks after 1992 has contributed to a better control of the dissemination of HCV infection. Because of the predominance of genotype 1, these patients belong to a group requiring special treatment, with a probable indication of new therapeutic options against HCV.

Hepatitis C virus genetic variability: pathogenic and clinical implications

HCV is variable because of the properties of the viral RdRp, high levels of replication, and large population sizes. The Darwinian evolution of HCV has been characterized by the emergence of the HCV genotypes, including six main types and a large number of subtypes. The study of HCV genotype epidemiology provides useful information on the worldwide HCV epidemics. The HCV genotype is an important predictor of the response to IFN-alpha-based antiviral therapy, and genotype determination is currently used to tailor treatment indications. In addition, HCV circulates and behaves in infected individuals as mixtures of closely related but distinct viral populations referred to as quasispecies. This particular nature of the virus influences its transmission, the pathogenesis of liver disease and extra-hepatic manifestations, and the outcome during and after antiviral therapy or after transplantation for HCV-related end-stage liver disease. Further studies are needed to understand better the implications of HCV quasispecies diversity in the pathophysiology of HCV infection.

Prevalence of blood-borne infectious diseases in blood donors in Ghana

Transfusion-transmissible infections among 808 blood donors in Ghana were investigated in 1999. Antibody seroprevalences of 3.8, 0.7, 8.4, and 13.5%, respectively, for human immunodeficiency virus, human T-cell lymphotrophic virus type 1, hepatitis C virus (HCV), and Treponema pallidum were obtained. The seroprevalence of HCV infection was confirmed to be 0.9% after supplementary testing, and the transfusion risk potential of these pathogens was demonstrated.

Epidemiology of chronic hepatitis C virus infection in sub-Saharan Africa

Hepatitis C virus (HCV) is a major cause of chronic liver disease in the world. The WHO estimates that 3% (170 million) of the world's population are chronically infected with HCV. Sub-Saharan Africa is of great interest because it is reported to have the highest HCV prevalence rate (5.3%), and a concurrent HIV epidemic. In our review of the published literature we found consistent evidence of high HCV prevalence in many countries of Africa. We estimate the overall prevalence of HCV in Sub-Saharan Africa is 3.0%. The central African region has the highest estimated prevalence of 6%, west Africa has an estimated prevalence of 2.4%, and southern and east Africa with the lowest estimated prevalence of 1.6%. Given low sexual transmission of HCV and infrequency of intravenous drug use in Sub-Saharan Africa, iatrogenic causes of HCV transmission need to be further evaluated.

Hepatitis C: an epidemiological review

The aim of the study was to analyse the current literature regarding the mode of transmission of HCV and its global prevalence in different groups of people. A systematic review of the literature on the epidemiology of hepatitis C from 1991 to 2000 using computerized bibliographic databases which include Medline, Current Content and Embase. The prevalence of hepatitis C virus (HCV) varies tremendously in different parts of the world, with the highest incidence in the Eastern parts of the globe compared with the Western parts. Furthermore, certain groups of individuals such as intravenous drug users are at increased risk of acquiring this disease irrespective of the geographical location. Although the main route of transmission is via contaminated blood, curiously enough in up to 50% of the cases no recognizable transmission factor/route could be identified. Therefore, a number of other routes of transmission such as sexual or household exposure to infected contacts have been investigated with conflicting results. Hepatitis C infection is an important public health issue globally. Better understanding of routes of transmission will help to combat the spread of disease. In order to prevent a world wide epidemic of this disease, urgent measures are required to (i) develop a strategy to inform and educate the public regarding this disease and (ii) expedite the efforts to develop a vaccine.

Epidemiology and prophylaxis of viral hepatitis: a global perspective

BACKGROUND

Viral hepatitis with various forms of acute and chronic liver disease as potential and ultimately fatal sequelae presents a public health problem worldwide.

METHODS

Recent published reports on the global epidemiology and prophylaxis of viral hepatitis were reviewed.

RESULTS

With the advances in novel technologies, eight distinct types of hepatitis virus have been described: Hepatitis A, B, C, D, E, G, TT and SEN viruses. Hepatitis A and E viruses are transmitted by the fecal-oral route and do not induce a chronic carrier state. Due to major changes in epidemiology of hepatitis A virus their significance is more pronounced in areas of intermediate endemicity. Since the available hepatitis A vaccine is rather expensive, cost-benefit studies should be performed with emphasis on the area under consideration or specialized vulnerable groups. Parenterally transmitted hepatitis B and C viruses are major causes of chronic liver disease, including cirrhosis, hepatocellular carcinoma and end-stage liver failure. Hepatitis D virus is unable to replicate on its own, it requires an established hepatitis B virus infection to be able to replicate. Since its introduction, hepatitis B vaccine has been widely used leading to a significant decrease in HBV infection in countries with universal vaccination. Hepatitis G and TT viruses have been characterized within the latter part of the past decade but their significance as to the causation of human liver disease has yet to be elucidated. Likewise, the precise impact of the most recently described SEN virus isolated from patients with post-transfusion hepatitis awaits further studies.

CONCLUSIONS

In the course of this review, we present the situation and focus on research activities emphasizing epidemiology and prevention of the various forms of viral hepatitis.

Hepatitis B and C infections, human immunodeficiency virus and other sexually transmitted infections among women of childbearing age in Côte d'Ivoire, West Africa

Few studies have been conducted in developing countries to estimate the prevalence of hepatitis C virus (HCV) infection and its association with human immunodeficiency virus (HIV) and other sexually transmitted diseases (STDs). We have screened for hepatitis B virus (HBV) and HCV markers 200 HIV-1-positive, 23 HIV-2-positive and 206 HIV-negative women attending gynaecology clinics in 1995/96 in Abidjan, Côte d'Ivoire, a sample selected among 2198 consecutive consultants. Taking into account the prevalence of 21.7% for HIV in this population, the overall prevalence of anti-HBV core antibody was 81.6%, that for hepatitis B surface antigen was 9.9% and for HCV antibody was 3.3%. HIV infection and other STDs were not associated with HBV or HCV markers. Moreover, HBV and HCV markers were not statistically associated. Our results confirm the high prevalence of HIV in Abidjan and the endemic situation of HBV infection. Furthermore, HCV infection is not infrequent in this developing country setting, not explained by sexual transmission.

Reconstructing the origins of human hepatitis viruses

Infections with hepatitis B and C viruses (HBV, HCV) are widespread in human populations throughout the world, and are major causes of chronic liver disease and liver cancer. HBV, HCV and the related hepatitis G virus or GB virus C (referred to here as HGV/GBV-C) are capable of establishing persistent, frequently lifelong infections characterized by high levels of continuous replication. All three viruses show substantial genetic heterogeneity, which has allowed each to be classified into a number of distinct genotypes that have different geographical distributions and associations with different risk groups for infection. Information on their past transmission and epidemiology might be obtained by estimation of the time of divergence of the different genotypes of HCV, HBV and HGV/GBV-C using knowledge of their rates of sequence change. While information on the latter is limited to short observation periods and is therefore subject to considerable error and uncertainty, the relatively recent times of origin for genotype of each virus predicted by this method (HCV, 500-2000 years; HBV, 3000 years; HGV/GBV-C, 200 years) are quite incompatible with their epidemiological distributions in human populations. They also cannot easily be reconciled with the recent evidence for species-associated variants of HBV and HGV/GBV-C in a range of non-human primates. The apparent conservatism of viruses over long periods implied by their epidemiological distributions instead suggests that nucleotide sequence change may be subject to constraints peculiar to viruses with single-stranded genomes, or with overlapping reading frames that defy attempts to reconstruct evolution according to the principles of the 'molecular clock'. Large population sizes and intense selection pressures that optimize fitness may be additional factors that set virus evolution apart from that of their hosts.

The epidemic behavior of the hepatitis C virus

Hepatitis C virus (HCV) is a leading worldwide cause of liver disease. Here, we use a new model of HCV spread to investigate the epidemic behavior of the virus and to estimate its basic reproductive number from gene sequence data. We find significant differences in epidemic behavior among HCV subtypes and suggest that these differences are largely the result of subtype-specific transmission patterns. Our model builds a bridge between the disciplines of population genetics and mathematical epidemiology by using pathogen gene sequences to infer the population dynamic history of an infectious disease.

The origin and evolution of hepatitis viruses in humans

The spread and origins of hepatitis C virus (HCV) in human populations have been the subject of extensive investigations, not least because of the importance this information would provide in predicting clinical outcomes and controlling spread of HCV in the future. However, in the absence of historical and archaeological records of infection, the evolution of HCV and other human hepatitis viruses can only be inferred indirectly from their epidemiology and by genetic analysis of contemporary virus populations. Some information on the history of the latter may be obtained by dating the time of divergence of various genotypes of HCV, hepatitis B virus (HBV) and the non-pathogenic hepatitis G virus (HGV)/GB virus-C (GBV-C). However, the relatively recent times predicted for the origin of these viruses fit poorly with their epidemiological distributions and the recent evidence for species-associated variants of HBV and HGV/GBV-C in a wide range of non-human primates. The apparent conservatism of viruses over long periods implied by these latter observations may be the result of constraints on sequence change peculiar to viruses with single-stranded genomes, or with overlapping reading frames. Large population sizes and intense selection pressures that optimize fitness may be the factors that set virus evolution apart from that of their hosts.

Seroepidemiology of TT virus, GBC-C/HGV, and hepatitis viruses B, C, and E among women in a rural area of Tanzania

The seroprevalence and determinants of hepatitis B, C, and E virus infection, and of GBV-C/hepatitis G virus and TT virus infection were investigated among women from a rural area of northeastern Tanzania. High seroprevalence rates were found for TTV (74%), HBV (74%), and GBV-C/HGV (35%), whereas 7% of the women had evidence of HCV and HEV infection. The majority of TTV DNA sequences in the study population belonged to the genotypes 1 or 2. One sequence seems to represent a new subtype of genotype 4. The GBV-C/HGV sequences either belonged to the genomic Group 1b or to the recently described Group 4. In multivariate analysis, the detection of TTV DNA was associated significantly with a larger number of children in the household and with older age. A history of injections of contraceptive hormones was an independent risk factor for HCV infection. The findings on TTV are consistent with fecal-oral transmission, and recurrent infections may occur in adults.

Molecular heterogeneity and new subtypes of HCV genotype 4

The subtype distribution of HCV genotype 4 was studied in two different African countries, Egypt and Tanzania. The HCV isolates were obtained from epidemiological studies involving, respectively, 135 hepatopatic patients and 1043 pregnant women and outpatients. Sequence comparison and phylogenetic analysis of the NS5b genome region (nt 8327-8499) were performed. Fourteen out of 18 isolates from Egypt, but only 3 out of 6 isolates from Tanzania clustered in the same branch of subtype 4a. Three new proposed subtypes have been identified. The first includes 1 isolate from Egypt (EGY15); the second, 2 isolates from Egypt (EGY193 and EGY44) and 2 isolates from Tanzania (D776, D61); and the third, 1 isolate from Egypt (EGY47) and 1 isolate from Tanzania (D70). These isolates cluster in branches different from any other, corresponding to a known subtype of genotype 4. In conclusion, remarkable genetic heterogeneity has been found among genotype 4 isolates simultaneously circulating in a restricted area. This was particularly observed in the study performed in Tanzania. Potential concern about the sensitivity of diagnostic assays and possible implications in the development of future vaccines have been stressed.