First report of occult hepatitis B infection among ART naïve HIV seropositive individuals in Maputo, Mozambique

24-month outcomes after switching to Dolutegravir/Lamivudine in people living with HIV and HBcAb positivity at the Beijing Ditan Hospital in China

BACKGROUND

Dolutegravir/lamivudine (DTG/3TC) is a recommended therapy regimen for hepatitis B surface antigen (HBsAg)-negative people living with HIV (PLWH) who have achieved HIV virological suppression or are treatment-naïve. However, this may overlook the impact of occult hepatitis B infection on HIV suppression, which mainly present as hepatitis B core antibody (HBcAb) positive but HBsAg negative. We aim to assess the effect of HBcAb positivity on HIV suppression among PLWH who had switched to DTG/3TC.

METHODS

A retrospective study was conducted including 127 HBcAb-positive and 474 HBcAb-negative PLWH (all were HBsAg negative) who had switched to DTG/3TC at the Beijing Ditan Hospital in China. HIV-RNA suppression was compared pre-switch (not baseline), at switch, and at 12&24 months post-switch, across three categories: (1) target not detected (TND); (2) HIV RNA < 40 cp/mL; (3) blip. Virological suppression included TND and HIV RNA < 40 cp/mL. Epidemiological (gender, age) and clinical data (CD4 count, HIV viral load, etc.) were extracted from the hospital information system. A p-value < 0.05 was considered statistically significant.

RESULT

HBcAb-positive PLWH were older at DTG/3TC switch (median age: 41 vs. 36 years old, p < 0.001) and had lower nadir CD4 counts (median nadir CD4 counts: 255 vs. 295, p = 0.011). No difference in TND and HIV RNA < 40 cp/mL was present in the two groups at the switch (HBcAb-positive and -negative: 86.6% vs. 88.8%, 12.6% vs. 10.5%, p = 0.789). Similar HBcAb-positive compared with -negative PLWH resulted in TND at 12&24 months post-switch: 91.4% vs. 91% (p = 0.522) and 88.4% vs. 92.7% (p = 0.249), respectively. Consistent result was observed in HIV RNA < 40 cp/mL.

CONCLUSION

In the 24-month follow-up after switching to DTG/3TC, HBcAb positivity was not significantly associated with HIV virological suppression.

Genetic diversity and occult hepatitis B infection in Africa: A comprehensive review

BACKGROUND

Occult hepatitis B infection (OBI) is a globally prevalent infection, with its frequency being influenced by the prevalence of hepatitis B virus (HBV) infection in a particular geographic region, including Africa. OBI can be transmitted through blood transfusions and organ transplants and has been linked to the development of hepatocellular carcinoma (HCC). The associated HBV genotype influences the infection.

AIM

To highlight the genetic diversity and prevalence of OBI in Africa.

METHODS

This systematic review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines and involved a comprehensive search on PubMed, Google Scholar, Science Direct, and African Journals Online for published studies on the prevalence and genetic diversity of OBI in Africa.

RESULTS

The synthesis included 83 articles, revealing that the prevalence of OBI varied between countries and population groups, with the highest prevalence being 90.9% in patients with hepatitis C virus infection and 38% in blood donors, indicating an increased risk of HBV transmission through blood transfusions. Cases of OBI reactivation have been reported following chemotherapy. Genotype D is the predominant, followed by genotypes A and E.

CONCLUSION

This review highlights the prevalence of OBI in Africa, which varies across countries and population groups. The study also demonstrates that genotype D is the most prevalent.

Hepatitis B virus genotypes and drug resistance mutations circulating in blood donors in Beira, Mozambique

Hepatitis B virus (HBV) infects nearly 300 million people and is the leading cause of hepatitis and hepatocellular carcinoma worldwide. Despite the high burden of HBV in sub-Saharan Africa, countries such as Mozambique have limited data available on circulating HBV genotypes and the presence of drug resistance mutations. Blood donors from Beira, Mozambique were tested for HBV surface antigen (HBsAg) and HBV DNA at the Instituto Nacional de Saúde in Maputo, Mozambique. Regardless of HBsAg status, donors with detectable HBV DNA were evaluated for HBV genotype. PCR was performed with primers amplifying a 2.1-2.2 kilobase fragment of the HBV genome. PCR products were submitted for next generation sequencing (NGS), and consensus sequences were evaluated for HBV genotype, recombination, and the presence or absence of drug resistance mutations. Of the 1281 blood donors tested, 74 had quantifiable HBV DNA. The polymerase gene could be amplified from 45 of 58 (77.6%) individuals with chronic HBV infection and 12 of 16 (75%) with occult HBV infection. Among these 57, 51 (89.5%) sequences belonged to HBV genotype A1, while 6 (10.5%) were HBV genotype E. All genotype E sequences were E/A recombinants, and clustered separately from other genotype E references. Genotype A samples had a median viral load of 637 IU/mL, while genotype E samples had a median viral load of 476,084 IU/mL. No drug resistance mutations were observed in the consensus sequences. The current study demonstrates the genotypic diversity of HBV in blood donors in Mozambique, but the absence of dominant (consensus) drug resistance mutations. Studies in other at-risk populations are essential for understanding the epidemiology, risk of liver disease, and likelihood of treatment resistance in resource-limited settings.

Epidemiology of occult hepatitis B and C in Africa: A systematic review and meta-analysis

BACKGROUND

Occult hepatitis B (OBI) and C (OCI) infections lead to hepatic crises including cases of liver cirrhosis and even hepatocellular carcinoma (HCC). OBI and OCI also pose a significant problem of their transmissibility. This study aimed to assess the overall prevalence of OBI and OCI in the African continent, a region highly endemic for classical hepatitis B and C viruses.

METHODS

For this systematic review and meta-analysis, we searched: PubMed, Web of Science, African Journal Online and African Index Medicus for published studies on the prevalence of OBI and OCI in Africa. Study selection and data extraction were performed by at least two independent investigators. Heterogeneity (I²) was assessed using the χ² test on the Cochran Q statistic and H parameters. Sources of heterogeneity were explored by subgroup analyses. This study was registered in PROSPERO, with reference number CRD42021252772.

RESULTS

We obtained 157 prevalence data for this meta-analysis, from 134 studies for OBI prevalence; 23 studies on OCI prevalence, and a single study on the OBI case fatality rate. The overall estimate for the prevalence of OBI was 14.8% [95% CI = 12.2-17.7] among 18579 participants. The prevalence of seronegative OBI and seropositive OBI was 7.4% [95% CI = 3.8-11.8] and 20.0% [95% CI = 15.3-25.1] respectively. The overall estimate for the prevalence of OCI was 10.7% [95% CI = 6.6-15.4] among 2865 participants. The pooled prevalence of seronegative OCI was estimated at 10.7% [95%CI = 4.8-18.3] and that of seropositive OCI at 14.4% [95%CI = 5.2-22.1]. In Sub-group analysis, patients with malignancies, chronic hepatitis C, and hemodialysis had a higher OCI prevalence. While those with malignancies, liver disorders, and HIV positive registered highest OBI prevalence.

CONCLUSION

This review shows a high prevalence of OBI and OCI in Africa, with variable prevalence between countries and population groups.

Prevalence and Clinical Significance of Occult Hepatitis B Infection in The Gambia, West Africa

BACKGROUND

Prevalence and clinical outcomes of occult hepatitis B infection (OBI) have been poorly studied in Africa.

METHODS

Using the PROLIFICA cohort, we compared the prevalence of OBI between hepatitis B surface antigen (HBsAg)-negative healthy adults screened from the general population (controls) and HBsAg-negative patients with advanced liver disease (cases), and estimated the population attributable fraction for the effect of OBI on advanced liver disease.

RESULTS

OBI prevalence was significantly higher among cases (15/82, 18.3%) than controls (31/330, 9.4%, P = .03). After adjusting for age, sex, and anti-hepatitis C virus (HCV) serology, OBI was significantly associated with advanced liver disease (odds ratio, 2.8; 95% confidence interval [CI], 1.3-6.0; P = .006). In HBsAg-negative people, the proportions of advanced liver disease cases attributable to OBI and HCV were estimated at 12.9% (95% CI, 7.5%-18.1%) and 16.9% (95% CI, 15.2%-18.6%), respectively.

CONCLUSIONS

OBI is endemic and an independent risk factor for advanced liver disease in The Gambia, West Africa. This implies that HBsAg-negative people with liver disease should be systematically screened for OBI. Moreover, the impact of infant hepatitis B immunization to prevent end-stage liver disease might be higher than previous estimates based solely on HBsAg positivity.

Detection of occult hepatitis B virus infection among subjects with isolated hepatitis B core antibodies: Results from a 3-year survey in an Italian tertiary-care hospital

BACKGROUND

Hepatitis B virus (HBV) infection causes hepatitis, liver cirrhosis, hepatocellular carcinoma, and death. This study examines the subjects with isolated anti-HBV core antigen antibody (anti-HBcAg), a pattern characterized by the persistent HBV carriage in the absence of HBV surface antigen (HBsAg) and anti-HBsAg antibody.

METHODS

Based on medical orders, from 2017 to 2019, serological and molecular assays were performed on serum/plasma samples of 33,048 subjects (71.4% Italians, 28.6% foreigners), who referred to the Virology Unit of the University-Hospital of Parma (Northern Italy) for the laboratory diagnosis of HBV infection.

RESULTS

The seroprevalence was 4.6% for HBsAg and 11% for anti-HBcAg. The occurrence of the isolated anti-HBcAg status was 3.1%, with higher frequency in males than in females (66.3% vs. 33.7%, P < 0.0001), in Italians than in foreigners (54.8% vs. 45.2%, P < 0.001), and in outpatients than in inpatients (57.4% vs. 42.6%, P < 0.0001). Foreigners with isolated anti-HBcAg came mostly from Africa (67.9%) and Eastern Europe (26.2%). Among subjects with isolated anti-HBcAg, 14.8% had occult HBV infection, 26.3% hepatitis C virus co-infection, 2% human immunodeficiency virus co-infection, and 3.3% both of these latter co-infections.

CONCLUSIONS

The anti-HBcAg assay accurately evaluates the HBV exposure; subjects with isolated anti-HBcAg antibody should be further analysed for HBV DNA. The HBV infection prevalence in Italy is increasing, due to growing migratory flows from endemic areas.

Prevention of mother-to-child transmission of hepatitis B virus in antenatal care and maternity services, Mozambique

Objective

To pilot an intervention on the prevention of mother-to-child transmission (PMTCT) of hepatitis B virus (HBV) in an antenatal care and maternity unit in Maputo, Mozambique, during 2017–2019.

Methods

We included HBV in the existing screening programme (for human immunodeficiency virus (HIV) and syphilis) for pregnant women at their first consultation, and followed mother–child dyads until 9 months after delivery. We referred women who tested positive for hepatitis B surface antigen (HBsAg) for further tests, including hepatitis B e antigen (HBeAg) and HBV viral load. According to the results, we proposed tenofovir for their own health or for PMTCT. We administered birth-dose HBV vaccine and assessed infant HBV status at 9 months.

Findings

Of 6775 screened women, 270 (4.0%) were HBsAg positive; in those for whom data were available, 24/265 (9.1%) were HBeAg positive and 14/267 (5.2%) had a viral load of > 200 000 IU/mL. Ninety-eight (36.3%) HBsAg-positive women were HIV coinfected, 97 of whom were receiving antiretroviral treatment with tenofovir. Among HIV-negative women, four had an indication for tenofovir treatment and four for tenofovir PMTCT. Of 217 exposed liveborn babies, 181 (83.4%) received birth-dose HBV vaccine, 160 (88.4%) of these < 24 hours after birth. At the 9-month follow-up, only one out of the 134 tested infants was HBV positive.

Conclusion

Our nurse-led intervention highlights the feasibility of integrating PMTCT of HBV into existing antenatal care departments, essential for the implementation of the triple elimination initiative. Universal birth-dose vaccination is key to achieving HBV elimination.

Occult Hepatitis B Virus Infection among β-Thalassemia Major Patients in Ahvaz City, Iran

Occult Hepatitis B Infection (OBI) is a critical risk factor for triggering post-transfusion hepatitis (PTH), cirrhosis, hepatocellular carcinoma, and hepatitis B virus (HBV) reactivation, which β-thalassemia major (BTM) patients are at risk of it due to multiple blood transfusions. This study was aimed at determining the prevalence of OBI among BTM patients from Khuzestan Province, Iran. In this cross-sectional study, 90 thalassemia patients, who have received blood 36 to 552 times, participated referred to the Shafa hospital of Ahvaz city from January 2018 to April 2019. ELISA for determining serological markers (HBsAg, anti-HBc, anti-HBs, and anti-HCV) and real-time PCR for detecting HBV-DNA were performed; Nested PCR was conducted for DNA sequencing and determining the genotype of OBI case. Phylogenetic and statistical analyses were done by R package. Of 90 subjects enrolled in this study; 95.5% (86/90) were HBsAg negative, and the frequency of OBI among them was 1.16% (1/86). The anti-HBs, anti-HBc, and anti-HCV were detected in 80.00%, 7.78%, and 12.2% of patients, respectively. HBV-DNA was assessed at four HBsAg-positive subjects as well, and all of them were negative. The phylogenetic analysis showed that the detected HBV DNA in the OBI case belongs to the genotype D. This research, for the first time, demonstrated that OBI is present among β-thalassemia patients in Iran. Also, further studies are necessary to determine the actual prevalence of OBI among BTM patients in Iran to decisions concerning OBI screening, especially in transfusion centers.

Occult Hepatitis B virus (HBV) infection and challenges for hepatitis elimination: A literature review

Occult hepatitis B infection (OBI) is characterized by the detection of hepatitis B virus (HBV) DNA in serum or liver but negativity for hepatitis B surface antigen. OBI, which is thought to be maintained by host, immunological, viral and/or epigenetic factors, is one of the most challenging clinical features in the study of viral hepatitis. Currently, there is no validated detection test for OBI. It is believed that OBI is widely distributed throughout the world, with a higher prevalence in populations at high-risk HBV, but the detailed worldwide prevalence patterns are unknown. We conducted a survey of recently published studies on OBI rates across all continents. High prevalence rates of OBI are observed in some specific groups, including patients with hepatitis C virus, human immunodeficiency virus co-infection or hepatocellular carcinoma. In 2016, the World Health Organization adopted strategies to eliminate viral hepatitis by 2030, but the difficulties in detecting and treating OBI currently challenge this goal. Subjects with OBI can transmit HBV, and episodes of reactivation can occur. Further studies to understanding the mechanisms that drive the development of OBI are needed and can contribute to efforts at eliminating viral hepatitis.

Prevalence of Overt and Occult Hepatitis B Virus Infection among HIV-Positive People Referring to Consultation Center for Behavioral Diseases, Kurdistan Province, Iran

Background

Based on evidence, human immunodeficiency virus (HIV) and hepatitis B virus (HBV) have common transmission routes; co-infection of HBV/HIV can dramatically increase disease progression. The present study aimed to determine the prevalence of overt HBV infection and occult hepatitis B virus infection (OBI) in HIV-positive people.

Methods

In this descriptive study, whole blood samples were collected from 184 HIV-positive subjects referring to the Consultation Center for Behavioral Diseases, Sanandaj, Iran, during 2014 to 2016. ELISA was used for the determination of HBV serologic markers (hepatitis B surface antigen [HBsAg] and antibodies to hepatitis B virus core antigen [anti-HBc]). To evaluate OBI, DNA was extracted only from HBsAg-negative and anti-HBc-positive samples and tested for HBV DNA by real-time PCR. Test results and patients’ data were analyzed by SPSS software.

Results

The mean age of the study population was 39.2 ± 9.4 (SD) years, of whom 140 (76%) were male. Overall, 43 (23.3%) samples were positive for HBsAg (overt HBV infection), and 50 (27.2%) for anti-HBc. Among 31 HBsAg-negative and anti-HBc-positive samples (suspected OBI), one (3.2%) sample was positive for HBV DNA (verified seropositive OBI). HBV infection was higher among males (n = 37; 86.05%), jobless people (n = 23; 53.49%), and those with an injection HIV transmission route (n = 32; 74.43%).

Conclusion

We observed a high prevalence of overt HBV and one OBI among the study population. A serologic marker such as anti-HBc indicates resolved or past HBV infection. Molecular screening for HBV is valuable for the management of HIV-infected people.

Occult hepatitis B infection in Turkish HIV-infected patients: A multicentre, retrospective, cross-sectional study, Schindler study

OBJECTIVE

Occult hepatitis B infection (OHBI) appears to have a higher prevalence in populations at high risk for hepatitis B virus (HBV) infection with concomitant liver disease. The aim was to assess the prevalence of OHBI in a sample of human immunodeficiency virus -1 positive and HBV surface antigen-negative (HIV-1+/HBsAg-) Turkish patients.

METHODS

Ten centres in Turkey were included in the study. Patients were selected on the basis of a power calculation with a known population size of HIV-positive patients and a reported prevalence of OHBI. Gender, age, occupation, place of residence, treatment and clinical status, and laboratory results, including immunodeficiency panel, antibody tests, hemogram, biochemistry, and coagulation studies were evaluated retrospectively.

RESULTS

The number of HIV-infected patients followed in these centres was 3172 and the sample population numbered 278. All 278 were HBsAg negative. The mean age of the sample was 37.2 ± 13.1 years and 235 (84.5%) were male. All but one patient (99.6%) had been treated with antiretroviral therapy. Of the 278 patients, 169 (60.6%) were positive for Anti-HBs and 125 (44.8%) were positive for Anti-HBc IgG. HIV RNA was detected in 203/278 (73%) of the patients. Four HBV DNA (1.4%) were diagnosed with OHBI. There was no significant difference in hemogram, hemoglobin or bilirubin concentrations in those with OHBI compared with the other patients.

CONCLUSION

In a representative sample of HIV+ patients from 10 Turkish centres, the prevalence of OHBI was found to be 1.4%. In HIV positive patients, it is important to identify those with OHBI for optimal clinical management and prognosis.

Occult hepatitis B virus infection in a Kenyan cohort of HIV infected anti-retroviral therapy naïve adults

BACKGROUND

Occult hepatitis B virus (HBV) infection (OBI) is a phase of HBV infection characterised by the presence of HBV DNA in the absence of detectable hepatitis B surface antigen (HBsAg). OBI is of concern in the HIV-infected due to high prevalence and risk of HBV reactivation. The prevalence and clinico-demographic characteristics of OBI in anti-retroviral therapy (ART) naïve HIV infected adults in Kenya is unknown.

METHODS

A cross sectional study carried was out at three sites in Kenya. HIV infected ART naïve adults were enrolled and demographic data collected. Blood samples were assayed for HBsAg, HBV DNA, alanine aminotransferase, aspartate aminotransferase, antibodies to hepatitis B surface antigen (anti-HBs) and hepatitis B core antigen (anti-HBc). Data on CD4 count, HIV viral load and platelet count were obtained from medical records.

RESULTS

Of 208 patients, 199 (95.7%) did not report HBV vaccination, 196 (94.2%) were HBsAg negative, 119 (57.2%) had no HBV markers, 58 (27.9%) had previous HBV infection (anti-HBc positive) and 11 (5.3%) had OBI. All 11 (100%) OBI patients were anti-HBc positive. OBI patients comprised 19.0% of HBsAg negative, anti-HBc positive patients. There was no difference in clinico-demographic characteristics between the overt HBV, OBI and HBV negative patients.

CONCLUSION

This was the first study on OBI in ART naïve HIV infected adults in Kenya. The lower OBI prevalence compared to other sub-Saharan African countries could be attributed to lower HBV exposure. Most patients were HBV unexposed and unimmunized, outlining the need to implement guideline recommended immunization strategies.

Molecular and serological characterization of occult hepatitis B among blood donors in Maputo, Mozambique

BACKGROUND

Occult hepatitis B virus (HBV) - characterized by the absence of detectable HBsAg in the presence of HBV DNA - represents a potential threat for blood safety.

OBJECTIVES

This study was conducted with the aim to investigate the serological and molecular characterization of occult HBV infection (OBI) among blood donors in Mozambique.

METHODS

1,502 blood donors were tested for HBsAg. All HBsAg-negative individuals were tested for HBV DNA. Antibodies against HBV core, surface and HBe antigen (anti-HBc, anti-HBs, HBeAg) were measured in HBV DNA positive individuals.

FINDINGS

1435 serum samples were HBsAg negative and 16 positive for HBV DNA, 14 confirmed to have OBI, corresponding to a frequency of 0.98%. Of the 14 OBI infections identified, 13/14 (92.8%) were positive for anti-HBc, 4/14 (28.5%) for anti-HBs, and no samples were reactive for HBeAg. Of the 14 OBI cases, nine samples (64.2%) were sequenced for the S/P region. Eight samples (88.9%) belonged to genotype A1 and one (11.1%) to genotype E. One escape mutation (T123A) associated with OBI and various amino acid substitutions for genotype A1 and E were observed.

MAIN CONCLUSIONS

Our results show the importance of using nucleic acid amplification test to detect occult hepatitis B infection in blood donors in Mozambique.

High frequency of HBV in HIV-infected prisoners in Mozambique

PURPOSE

The purpose of this paper is to determine the prevalence of hepatitis B virus (HBV) among 448 HIV-infected prisoners from 32 prisons in Mozambique.

DESIGN/METHODOLOGY/APPROACH

All HIV seropositive prisoners were screened for HBV.

FINDINGS

Of the 448 HIV seropositive prisoners, 51 (11.4 percent, 95%CI: 9.3-13.9 percent) were HBsAg-positive and was significantly higher in prisoners aged<25 years.

ORIGINALITY/VALUE

Data from this study show for the first time that the frequency of HBV among HIV-infected prisoners is high, suggesting that immediate interventions are needed during incarceration.

Prevalence and characteristics of occult hepatitis B virus infection in Japanese human immunodeficiency virus-infected patients

Occult hepatitis B virus (HBV) infection (OBI) is hepatitis B surface antigen (HBsAg) negative but with detectable HBV DNA. Although HIV infection has been reported to be a risk factor for OBI, the prevalence and clinical features of OBI in Japanese HIV infected patients have not been documented. This retrospective, single-center study was conducted to determine the prevalence and characteristic of OBI in Japanese antiretroviral therapy (ART) naïve HIV infected patients. OBI was defined as the presence of serum HBV DNA but without detectable HBsAg. Of the 147 ART naïve HIV infected patients, OBI was detected in 9 (6.1%) patients; 2 (4.3%) of 47 with both anti-HBs and anti-HBc positive, 6 (27.3%) of 22 with anti-HBc alone, and 1 (2.0%) of 50 with both anti-HBs and anti-HBc negative. The mean HBV DNA level was low at 28.7 ± 18.2 IU/mL. The proportion of OBI patients with anti-HBc alone was significantly higher than that of non-OBI patients (66.7% vs 14.5%, P = 0.001). In addition, the prevalence of AIDS (acquired immunodeficiency syndrome)-defining illnesses in the OBI group was significantly higher than in the non-OBI group (77.8% vs 35.5%, P = 0.001). No significant difference was found in the CD4 count or alanine aminotransferase levels of these two groups. This is the first study to reveal the prevalence and clinical features of OBI in Japanese HIV-infected patients. The persistence of anti-HBc alone and AIDS-defining illnesses were associated with the occurrence of OBI in these patients.

Screening for retroviruses and hepatitis viruses using dried blood spots reveals a high prevalence of occult hepatitis B in Ghana

Background:

Recent advances in antiviral therapy show potential for a cure and/or control of most human infections caused by hepatitis viruses and retroviruses. However, medical success is largely dependent on the identification of the large number of people unaware of these infections, especially in developing countries. Dried blood spots (DBS) have been demonstrated to be a good tool for collecting, storing and transporting clinical specimens from rural areas and limited-resource settings to laboratory facilities, where viral infections can be more reliably diagnosed.

Methods:

The seroprevalence and virological characterization of hepatitis B virus (HBV) and hepatitis C virus (HCV), as well as human retroviruses (HIV-1, HIV-2, human T-cell leukaemia virus type 1 [HTLV-1] and human T-cell leukaemia virus type 2 [HTLV-2]), were investigated in clinical specimens collected from DBS in Ghana.

Results:

A total of 305 consecutive DBS were collected. A high prevalence of chronic HBV (8.5%) and occult hepatitis B (14.2%) was found, whereas rates were lower for HIV-1, HTLV-1 and HCV (3.2%, 1.3% and 0.6%, respectively). HIV-2 and HTLV-2 were absent. CRF02_AG was the predominant HIV-1 subtype, whereas genotype E was the most frequent HBV variant.

Conclusions:

DBS are helpful in the diagnosis and virological characterization of hepatitis and retrovirus infections in resource-limited settings. The high rate of hepatitis B in Ghana, either overt or occult, is noteworthy and confirms recent findings from other sub-Saharan countries. This should encourage close clinical follow up and antiviral treatment assessment in this population, as well as universal HBV vaccine campaigns.

Hepatitis B virus infection

Hepatitis B virus (HBV) is a hepatotropic virus that can establish a persistent and chronic infection in humans through immune anergy. Currently, 3.5% of the global population is chronically infected with HBV, although the incidence of HBV infections is decreasing owing to vaccination and, to a lesser extent, the use of antiviral therapy to reduce the viral load of chronically infected individuals. The course of chronic HBV infection typically comprises different clinical phases, each of which potentially lasts for decades. Well-defined and verified serum and liver biopsy diagnostic markers enable the assessment of disease severity, viral replication status, patient risk stratification and treatment decisions. Current therapy includes antiviral agents that directly act on viral replication and immunomodulators, such as interferon therapy. Antiviral agents for HBV include reverse transcriptase inhibitors, which are nucleoside or nucleotide analogues that can profoundly suppress HBV replication but require long-term maintenance therapy. Novel compounds are being actively investigated to achieve the goal of HBV surface antigen seroclearance (functional cure), a serological state that is associated with a higher remission rate (thus, no viral rebound) after treatment cessation and a lower rate of cirrhosis and hepatocellular carcinoma. This Primer addresses several aspects of HBV infection, including epidemiology, immune pathophysiology, diagnosis, prevention and management.