Transfusion-associated Hepatitis Research Articles

Leveraging Donor Populations to Study the Epidemiology and Pathogenesis of Transfusion-Transmitted and Emerging Infectious Diseases

The tragedy of transfusion-associated hepatitis and HIV spurred a decades-long overhaul of the regulatory oversight and practice of blood transfusion. Consequent to improved donor selection, testing, process control, clinical transfusion practice and post-transfusion surveillance, transfusion in the United States and other high-income countries is now a very safe medical procedure. Nonetheless, pathogens continue to emerge and threaten the blood supply, highlighting the need for a proactive approach to blood transfusion safety. Blood donor populations and the global transfusion infrastructure are under-utilized resources for the study of infectious diseases. Blood donors are large, demographically diverse subsets of general populations for whom cross-sectional and longitudinal samples are readily accessible for serological and molecular testing. Blood donor collection networks span diverse geographies, including in low- and middle-income countries, where agents, especially zoonotic pathogens, are able to emerge and spread, given limited tools for recognition, surveillance and control. Routine laboratory storage and transportation, coupled with data capture, afford access to rich epidemiological data to assess the epidemiology and pathogenesis of established and emerging infections. Subsequent to the State of the Science in Transfusion Medicine symposium in 2022, our working group (WG), “Emerging Infections: Impact on Blood Science, the Blood Supply, Blood Safety, and Public Health” elected to focus on “leveraging donor populations to study the epidemiology and pathogenesis of transfusion-transmitted and emerging infectious diseases.” The 5 landmark studies span (1) the implication of hepatitis C virus in post-transfusion hepatitis, (2) longitudinal evaluation of plasma donors with incident infections, thus informing the development of a widely used staging system for acute HIV infection, (3) explication of the dynamics of early West Nile Virus infection, (4) the deployment of combined molecular and serological donor screening for Babesia microti, to characterize its epidemiology and infectivity and facilitate routine donor screening, and (5) national serosurveillance for SARS-CoV-2 during the COVID-19 pandemic. The studies highlight the interplay between infectious diseases and transfusion medicine, including the imperative to ensure blood transfusion safety and the broader application of blood donor populations to the study of infectious diseases.

The impact of nucleic acid testing as a blood donor screening method in transfusion-associated hepatitis C among children with bleeding disorders in Indonesia: a single-center experience.

BackgroundChildren with bleeding disorders, such as hemophilia and von Willebrand disease (VWD), have an increased risk of acquiring transfusion-transmitted infections (TTI). Screening methods to exclude blood donations that are at risk of transmitting infection from donors to recipients are critical to preventing disease transmission. Nucleic acid testing (NAT) is the latest blood donor-screening method. This study aimed to determine the incidence of hepatitis C virus (HCV) infection in children with hemophilia and VWD at Dr. Cipto Mangunkusumo Hospital with a history of blood transfusion before and after implementation of a NAT screening method.MethodsA cohort retrospective study was conducted on children aged 0‒18 years with bleeding disorders and a history of blood transfusion. In our center, all blood transfusions before 2015 were screened using non-NAT methods, while all blood transfusions were screened using NAT starting in 2015. Eligible patient characteristics were collected from medical records. From July to December 2019, blood samples were obtained from eligible patients for anti-HCV examination. HCV RNA examinations were performed on subjects with reactive anti-HCV results, and the relative risk was calculated.ResultsIn total, 108 eligible participants were included in this study. We observed that 91 (94.3%) patients had history of receiving non-NAT blood transfusions, while 17 (15.7%) patients received NAT-screened blood transfusions. The proportion of anti-HCV reactivity in the non-NAT group and that in the NAT group were 3.3% (3/91) and 0% (0/17), respectively.ConclusionNone of the patients exhibited reactivity to anti-HCV after implementing the NAT screening method.

Breakthroughs in hepatitis C research: from discovery to cure.

In the 1970s, an unknown virus was suspected for documented cases of transfusion-associated hepatitis, a phenomenon called non-A, non-B hepatitis. In 1989, the infectious transmissible agent was identified and named hepatitis C virus (HCV) and, soon enough, the first diagnostic HCV antibody test was developed, which led to a dramatic decrease in new infections. Today, HCV infection remains a global health burden and a major cause of liver cirrhosis, hepatocellular carcinoma and liver transplantation. However, tremendous advances have been made over the decades, and HCV became the first curable, chronic viral infection. The introduction of direct antiviral agents revolutionized antiviral treatment, leading to viral eradication in more than 98% of all patients infected with HCV. This Perspective discusses the history of HCV research, which reads like a role model for successful translational research: starting from a clinical observation, specific therapeutic agents were developed, which finally were implemented in national and global elimination programmes.

Reappraisal of screening strategy in hepatitis B surface antigen-negative blood donors: Correlation with hepatitis B virus-DNA quantification.

BACKGROUND:In spite of screening for hepatitis B surface antigen (HBsAg), transfusion-associated hepatitis B virus (TAHBV) infection remains a serious public health problem due to transmission of HBV in window period and occult HBV infection. To avoid TAHBV infection, some health-care facilities have started Hepatitis B core antibody test along with HBsAg, but this leads to a lot of potential donor rejection who are not HBV infected. Our aim is to find a new protocol of donor screening to prevent TAHBV without compromising blood availability.MATERIALS AND METHODS:A total of 88 HBsAg-negative anti-HBc total positive blood donors were included in this study. All samples were also tested for anti-HBs by enzyme immunoassay and for the presence of HBV-DNA viral load by real-time polymerase chain reaction.RESULTS:A total of 88 HBsAg negative and anti-HBc, total positive blood donors were tested for anti-HBs and HBV-DNA (Qn.). Among them, 76 donors (86.4%) (males 73 and females 3) were found to be positive for anti-HBs, while rest 12 (13.6%) showed no detectable antibody against HBsAg. HBV-DNA was found to be positive in 4 (7.7%) donor samples among 52 (60%) who have anti-HBs level <100 mIU/ml, while 36 (40%) donor samples were found to have >100 mIU/ml anti-HBs antibody with no detectable HBV-DNA.CONCLUSION:HBV-DNA should be implemented as a screening test of the blood donors to prevent TAHBV infection without potential donor rejection.

Low rates of transfusion-transmitted infection screening in chronically transfused adults with sickle cell disease.

Adults with sickle cell disease (SCD) on chronic transfusion therapy are exposed to a large volume of blood products, thus increasing their risk of transfusion-associated human immunodeficiency virus (HIV), hepatitis C (HCV), and hepatitis B (HBV). We performed a systematic chart review of chronically transfused SCD subjects at the Johns Hopkins Sickle Cell Center for Adults between October 2014 and September 2019 to determine our Center's adherence to the 2014 National Heart, Lung and Blood Institute (NHLBI) SCD guidelines for annual screening for Transfusion Transmitted infections (TTI) and assessed HBV immunity and HBV vaccination rates. The study included 85 subjects with a median age of 34 years (23-63); 52% were female. No subject received annual screening; 68 subjects (80%) were screened for HIV, 60 subjects (71%) for HCV and 53 subjects (62%) for HBV infections at least once in the study period. Of those screened, one patient was newly diagnosed with HCV infection, and none with HIV or HBV infection. Among 31 subjects tested for anti-Hepatitis B surface antibody, 16 subjects (52%) tested negative. Nineteen (20%) subjects had HBV vaccination documented. Low adherence to the NHLBI TTI screening guidelines, especially for HBV, highlights the resource intensiveness of this patient population. The low rates of anti-Hepatitis B surface antibody positivity highlight the need to confirm vaccination, provide boosters as indicated, and investigate the adults with SCD's immune response to HBV vaccination.

Transfusion-associated hepatitis E in a patient with refractory malignant lymphoma

Transfusion-associated hepatitis E in a patient with refractory malignant lymphoma

Hepatitis B Diagnosis in Blood Bank: Evaluation and Challenges

Hepatitis B virus (HBV) presents a higher residual risk of trans mission by transfusion than hepatitis C virus (HCV) or human immunodeficiency virus (HIV). While most infectious blood units are removed by screening for hepatitis B surface antigen (HBsAg), there is clear evidence that transmission by HBsAg-negative components occurs, in part, during the serolo gically negative window period, but more so during the late stages of infection. To encourage voluntary blood donation should be the first step of prevention. To reduce the risk of transfusion-associated hepatitis B, test for anti-HBc immunoglobulin M may be included in routine screening of donors’ blood, as it has been proved to be an excellent indicator of occult HBV during window period. However, awareness and education of donors regarding the modes of HBV transmission, a stringent one-to-one donor screening and increasing the voluntary donor base should also be implemented to minimize the rate of transfusion-associated hepatitis B.

Case report of a transfusion‐associated hepatitis A infection

Documented transfusion-associated hepatitis A (TAHA) is rare, and blood donors in the United States are not routinely screened for this infection. We report a case of TAHA associated with a donation made 8 days after a donor returned from a trip to South America. This is a review of donor and recipient records and a review of the literature. A donor developed symptoms of hepatitis 20 days after donation (28 days after returning from South America). The donor reported the illness 56 days after donation when contacted to schedule another visit. By this time, the red blood cell and frozen plasma components had been transfused. The recipient of the plasma, a 15-month-old female, tested positive for immunoglobulin M antibody to hepatitis A virus 43 days after transfusion. The recipient had displayed mild, nonspecific symptoms approximately 2 weeks after transfusion. Hospital infection control investigated the potential for further spread within the hospital because the recipient had been an inpatient for most of the posttransfusion period. The risk of transmission to other patients was determined to be negligible because the patient had been in isolation for other reasons. Family members, who included a health care professional, were counseled and offered prophylaxis. TAHA may be underrecognized. This case was identified only because of a donor report at the time of recruitment. Asymptomatic donor viremia has been documented in plasma donors. Although TAHA rarely results in severe disease, the risk it creates of secondary transmission especially within the hospital setting is not inconsequential.

The road not taken or how I learned to love the liver: A personal perspective on hepatitis history

The road not taken or how I learned to love the liver: A personal perspective on hepatitis history

Doğu Karadeniz Bölgesi Hepatit C Hastalarında Hepatit C Virusu Genotiplerinin Belirlenmesi

Hepatitis C virus (HCV), the major cause of transfusion-associated hepatitis, is an important public health problem in the world as well as in Turkey. HCV is grouped as six distinct genotypes and a large number of closely-related subtypes. Genotyping of HCV is an important tool for providing epidemiological data, prediction of prognosis, and optimization of antiviral therapy. This study was carried out to determine the distribution of HCV genotypes in hepatitis C patients residing in different provinces of the Eastern Black Sea Region, Turkey. A total of 304 HCV-RNA positive cases (151 male, 153 female; age range: 11-93 years, mean age: 55.2 ± 13.3 years) who were admitted to the Molecular Microbiology Unit of Department of Medical Microbiology, Karadeniz Technical University Faculty of Medicine, between January 2009 to December 2012, were included in the study. HCV genotypes were detected in plasma samples of the patients by using commercial assays [INNO-LiPA HCV II (Innogenetics, Belgium) or Abbott RealTime HCV Genotype II (Abbott Molecular Inc, USA)]. Due to the ambiguous genotyping results in some samples with these methods, an in-house multiplex polymerase chain reaction (PCR) assay with genotype-specific primers was also used in the study. Similar to the previous reports from Turkey, our results showed that four HCV genotypes (1, 2, 3, and 4) prevailed in the Eastern Black Sea Region and the predominant genotype and subtype were genotype 1 (92.8%) and 1b (87.5%), respectively. Distribution of genotypes were observed to vary according to the province. Prevalences of subtype 1a, genotype 2, 3, and 4 were noted as 5.3%, 1.6%, 4.9%, and 0.7%, respectively. Furthermore, the samples from Giresun, Gumushane and Bayburt provinces, which are relatively less immigrated, had higher genotype 1, and the prevalence rates in the region was affected by the presence of non-citizen residents. This study is the first report on distribution of HCV genotypes in chronic hepatitis C patients living in the provinces of Eastern Black Sea Region. Moreover, genotype-specific multiplex PCR assay could be useful in resolving certain methodological problems such as "ghost bands" encountered in line probe assay (LiPA) and multiple genotypes (including genotype 4) observed in real-time PCR during the characterization of HCV genotypes seen in Turkey.

Highly Sensitive Detection of Hepatitis B Virus Surface Antigen by Use of a Semiautomated Immune Complex Transfer Chemiluminescence Enzyme Immunoassay

The performance of hepatitis B surface antigen (HBsAg) screening assays is continuously improved to reduce the risk of transfusion-associated hepatitis B. In this study, a semiautomated immune complex transfer chemiluminescence enzyme immunoassay (ICT-CLEIA) for the detection of HBsAg, which is as sensitive as hepatitis B virus (HBV) DNA PCR, was developed; the ICT-CLEIA assay performance was compared with the performance of the Architect HBsAg QT assay and HBV DNA PCR. The specificities in the initial assay and after retesting were 99.50% (1,988/1,998 samples) and 99.95% (1,997/1,998 samples), respectively. The analytical detection limit was determined to be 0.2 mIU/ml using the 2nd International WHO HBsAg standard, and the cutoff value (0.5 mIU/ml) of the ICT-CLEIA assay was 8.0 standard deviations (SD) above the mean of the HBsAg-negative specimens. The ICT-CLEIA assay could detect HBsAg even in the presence of anti-HBs antibodies and demonstrated a 23.6-day-shorter window period using commercially available HBsAg seroconversion panels than the Architect HBsAg QT assay. Furthermore, the monitoring of the viral kinetics by the ICT-CLEIA assay and the HBV DNA PCR produced very similarly shaped curves during both the HBsAg seroconversion and reverse seroconversion periods. Therefore, the ICT-CLEIA assay may be useful not only for an earlier detection of HBV reactivation but also for the monitoring of hepatitis B patients.

G105 Profibrogenic Chemokines and Viral Evolution Predict Rapid Progression of Hepatitis C to Cirrhosis

The clinical presentation and outcomes of chronic hepatitis C are highly variable, and it is not possible to predict which individuals will rapidly evolve to severe fibrosis and liver failure. Using serial serum samples prospectively collected from 6 patients with transfusion-associated hepatitis C (followed from the day of transfusion for up to 30 years), we identified outcome-specific features that predict long-term disease severity. We found that stable or slowly progressive disease correlated with an earlier ALT peak and antibody seroconversion, transient control of viremia and significant induction of IFN- and MIP-1, all indicative of an effective, albeit insufficient, adaptive immune response. By contrast, rapidly progressive disease was associated with persistent and significant elevations of ALT and the profibrogenic chemokine MCP-1 (CCL-2), a major chemotactic factor for hepatic stellate cells, which play a central role in fibrogenesis. Rapidly progressive disease was also associated with greater viral diversity and divergence, and a higher rate of synonymous substitutions. Strikingly a strong genetic bottleneck occurred in all patients around one year post-infection. This study suggests that the long-term course of chronic hepatitis C is determined early in infection and that disease severity is predicted by the evolutionary dynamics of HCV and the level of MCP-1, a chemokine that appears critical to the induction of progressive fibrogenesis and, ultimately, the ominous complications of cirrhosis. In this proposed model for the pathogenesis of chronic HCV-related liver disease, rapid disease progression may result from an excess of soluble mediators of inflammation and fibrosis rather than from T-cell-mediated hepatotoxicity.

How to interpret borderline HCV antibody test results? A comparative study investigating four different anti-HCV assays

Introduction: The introduction of anti-HCV testing has been a milestone in medical history and markedly reduced transfusion-associated hepatitis C. Over the last 20 years, the performance of HCV antibody assays improved strikingly with sensitivities and specificities reaching >98% for most licensed tests. Still, a significant number of samples may yield borderline signal-to-cut-off ratios. Re-testing of samples and application of confirmatory recombinant blot assays or nucleic acid testing is time-consuming and costly. Moreover, false negative results should be avoided in particular in special risk groups such as immunocompromised patients. We here aimed to compare the performance of 4 licensed anti-HCV assays in samples with borderline signal-to-cut-off ratios obtained at a tertiary referral and transplant center.

Clinical approach to fever in the neurosurgical intensive care unit: Focus on drug fever.

As fever is one of the cardinal signs of infection, the presence of fever in a patient in the neurosurgical intensive care unit (NSICU) raises the question of whether it is infectious in etiology. Infectious and noninfectious causes of fever in the NSICU may be determined based upon assessment of clinical signs and symptoms, the degree of temperature elevation, the relationship of the pulse to the fever (e.g., an infectious process resulting in hyperpyrexia and bradycardia), and when the fever occurs (e.g., related to the length of stay in the NSICU). There are many noninfectious disorders which contribute to temperatures >102°F in the NSICU; these include drug fevers, deep vein thrombosis, phlebitis/pulmonary embolism, acute myocardial infarction, atelectasis, dehydration, acute gout flare, malignancy, acute pancreatitis, transfusion associated hepatitis, and hemorrhage. Infectious rather than noninfectious disorders, however, are more typically associated with high-grade fevers (>102°F.) in the NSICU, and nosocomial pneumonia, (synonymous with ventilator-associated pneumonia [VAP]), is the leading culprit, followed by nosocomial infections and Clostridium difficile.

Profibrogenic chemokines and viral evolution predict rapid progression of hepatitis C to cirrhosis

Chronic hepatitis C may follow a mild and stable disease course or progress rapidly to cirrhosis and liver-related death. The mechanisms underlying the different rates of disease progression are unknown. Using serial, prospectively collected samples from cases of transfusion-associated hepatitis C, we identified outcome-specific features that predict long-term disease severity. Slowly progressing disease correlated with an early alanine aminotransferase peak and antibody seroconversion, transient control of viremia, and significant induction of IFN-γ and MIP-1β, all indicative of an effective, albeit insufficient, adaptive immune response. By contrast, rapidly progressive disease correlated with persistent and significant elevations of alanine aminotransferase and the profibrogenic chemokine MCP-1 (CCL-2), greater viral diversity and divergence, and a higher rate of synonymous substitution. This study suggests that the long-term course of chronic hepatitis C is determined early in infection and that disease severity is predicted by the evolutionary dynamics of hepatitis C virus and the level of MCP-1, a chemokine that appears critical to the induction of progressive fibrogenesis and, ultimately, the ominous complications of cirrhosis.

Novel Approach for Detection of Hepatitis E Virus Infection in German Blood Donors

The risk of transfusion-transmitted hepatitis E virus (HEV) infections by contaminated blood products remains unknown. In the present study, we evaluated and compared different nucleic acid amplification technique (NAT) methods for the detection of HEV in blood components. Minipools of a total of 16,125 individual blood donors were screened for the presence of HEV RNA using the highly sensitive RealStar HEV RT-PCR kit, revealing a minimum detection limit of 4.66 IU/ml. Thirteen donors were HEV RNA positive (0.08%), and of these donors, only three already showed reactive IgM antibody titers. The detected HEV strains all belonged to genotype 3 and were most closely related to German HEV strains from wild boars and pigs as well as from human hepatitis E cases. Furthermore, HEV RNA and HEV-specific IgM and IgG titers were determined in 136 blood donors with elevated alanine aminotransferase (ALT) levels and in 200 donors without pathological findings. HEV RNA was not detectable, but 8.08% (elevated ALT) and 0.5% (nonelevated ALT) of donors showed reactive HEV IgM titers. The overall seroprevalence rate of HEV IgG amounted to 5.94% (elevated ALT, 5.88%; nonelevated ALT, 6.0%). The clinical relevance of transfusion-associated hepatitis E infection still requires further investigation. However, in connection with raising concerns regarding blood safety, our NAT method provides a sensitive possibility for HEV testing.

Assessment of disease progression in patients with transfusion-associated chronic hepatitis C using transient elastography.

To evaluate the relationship between liver stiffness and duration of infection in blood transfusion-associated hepatitis C virus (HCV) patients with or without hepatocellular carcinoma (HCC). Between December 2006 and June 2008, a total of 524 transfusion-associated HCV-RNA positive patients with or without HCC were enrolled. Liver stiffness was obtained noninvasively by using Fibroscan (Echosens, Paris, France). The date of blood transfusion was obtained by interview. Duration of infection was derived from the interval between the date of blood transfusion and the date of liver stiffness measurement (LSM). Patients were stratified into four groups based on the duration of infection (17-29 years; 30-39 years; 40-49 years; and 50-70 years). The difference in liver stiffness between patients with and without HCC was assessed in each group. Multiple linear regression analysis was used to determine the factors associated with liver stiffness. A total of 524 patients underwent LSM. Eight patients were excluded because of unsuccessful measurements. Thus 516 patients were included in the current analysis (225 with HCC and 291 without). The patients were 244 men and 272 women, with a mean age of 67.8 ± 9.5 years. The median liver stiffness was 14.3 kPa (25.8 in HCC group and 7.6 in non-HCC group). The patients who developed HCC in short duration of infection were male dominant, having lower platelet count, with a history of heavier alcohol consumption, showing higher liver stiffness, and receiving blood transfusion at an old age. Liver stiffness was positively correlated with duration of infection in patients without HCC (r = 0.132, P = 0.024) but not in patients with HCC (r = -0.103, P = 0.123). Liver stiffness was significantly higher in patients with HCC than in those without in each duration group (P < 0.0001). The factors significantly associated with high liver stiffness in multiple regression were age at blood transfusion (P < 0.0001), duration of infection (P = 0.0015), and heavy alcohol consumption (P = 0.043). Although liver stiffness gradually increases over time, HCC develops in patients with high stiffness value regardless of the duration of infection.

PREVENTION OF POST-TRANSFUSION HEPATITIS BY SCREENING OF ANTIBODY TO HEPATITIS B CORE ANTIGEN IN HEALTHY BLOOD DONORS

BackgroundTransfusion-associated hepatitis B viral infection continues to be a major problem in India even after adoption of mandatory screening for HBsAg by ELISA method. The high incidence of TAHBV is reported in patients receiving multiple transfusions.ObjectiveTo study the seroprevalence of hepatitis B core antibody among healthy voluntary blood donorsSubjects and MethodsThe study was conducted in the department of Transfusion Medicine of a tertiary care referral hospital. A total of 12,232 volunteers after passing through the stringent criteria were selected for blood donation. Donor samples were tested for all mandatory transfusion transmissible infections and anti HBc IgM (Monolisa HBc IgM PLUS:BIO-RAD, France). Reactive results were confirmed by repeat testing in duplicate. Donor data was analyzed using SPSS software and Chi-square test was used to calculate the significance of difference between the groups.ResultsA total of 12,232 healthy voluntary blood donors were recruited. Majority (93.4%) were males. Median age of donor population was 26 years (range: 18–60 years). Eighty six (0.7%) were positive for HBsAg, which comes under “low prevalence (<2%) zone” as per WHO. On screening for HBcAg Ig M, 15 (0.1%) were found to be positive and none were HBsAg reactive. There was no significance of difference in the mean age between reactive and non-reactive donors.ConclusionEvaluating the usefulness of anti-HBc screening is critical. Anti HBcAg IgM screening may be included in routine screening of donors as it is an indicator of occult HBV during window period. The cost and the unnecessary wastage of the blood units when they are positive for anti HBsAg along with the core antibody need to be studied.

Hepatitis E Virus (HEV) Strains in Serum Samples Can Replicate Efficiently in Cultured Cells Despite the Coexistence of HEV Antibodies: Characterization of HEV Virions in Blood Circulation

We recently developed a cell culture system for hepatitis E virus (HEV) in PLC/PRF/5 and A549 cells, using fecal specimens from HEV-infected patients. Since transfusion-associated hepatitis E has been reported, we examined PLC/PRF/5 and A549 cells for the ability to support replication of HEV in various serum samples obtained from 23 patients with genotype 1, 3, or 4 HEV. HEV progenies emerged in culture media of PLC/PRF/5 cells, regardless of the coexistence of HEV antibodies in serum but dependent on the load of HEV inoculated (31% at 2.0 x 10(4) copies per well and 100% at >or=3.5 x 10(4) copies per well), and were successfully passaged in A549 cells. HEV particles in serum, with or without HEV antibodies, banded at a sucrose density of 1.15 to 1.16 g/ml, which was markedly lower than that for HEV particles in feces, at 1.27 to 1.28 g/ml, and were nonneutralizable by immune sera in this cell culture system. An immuno-capture PCR assay of HEV virions treated with or without detergent indicated that HEV particles in serum are associated with lipids and HEV ORF3 protein, similar to those in culture supernatant. By immunoprecipitation, it was found that >90% of HEV particles in the circulation exist as free virions not complexed with immunoglobulins, despite the coexistence of HEV antibodies. These results suggest that our in vitro cell culture system can be used for propagation of a wide variety of HEV strains in sera from various infected patients, allowing extended studies on viral replication specific to different HEV strains.

The history of the “natural history” of hepatitis C (1968–2009)

In the late 1960's, only types A and B hepatitis were believed to exist, distinguished by circumstances of exposure and incubation periods. In the early 1970's, studies of transfusion recipients were begun with the belief that hepatitis B would be responsible should transfusion-associated hepatitis develop. After discovery of the viruses of hepatitis A and B, neither agent was found responsible, hence non-A, non-B (NANB) hepatitis. Initial follow-up of these cases showed that approximately 50% developed chronic hepatitis based on persistence of serum enzymes for at least 6 months. Approximately 15 years later, after the hepatitis C virus had been identified as the cause for NANB hepatitis, chronic hepatitis was found to develop more frequently as indicated by persistent viral infection in over 80% of infected adults but in only about 50% of infected children or young women. Follow-up over 2 to 4 decades indicated that many infected persons developed progressive hepatic fibrosis, sometimes culminating in cirrhosis and/or liver cancer. Long-term natural history studies have proved to be challenging because disease onset is often silent and progression extremely slow. Differing strategies have been used to determine the natural history, the descriptions and results of which are presented in this review.