International Research in Medical and Health Sciences | Vol. 1 | Issue 1 | September-October | 2018 Page | 8 (20 nm) and filamentous (22 nm) particles composed of HBsAg and host-derived lipids without viral nucleic acids; thus, these are noninfectious. [5] The complete HBV virion lipid envelops consist of HBsAg which encoded inner nucleocapsid composed of hepatitis B core antigen (HBcAg) with attached viral DNA and polymerase enzyme. The viral genome is 3.2 kb pairs; partially double- stranded circular DNA and polymerase enzyme are attached with the 5´end of the minus strand. [1] There are several open reading frames in the viral genome which encodes various proteins of HBV. The S region encodes HBsAg proteins, which further divided into three regions, pre-S1, pre-S2, and S. The core or C gene divided into two distinct regions of core and pre-core. Depending on the initiation of translation from the core and pre-core regions, C open reading frame encodes HBcAg or HBeAg. The P region consists of large polymerase protein gene which functionally divided into three forms, such as the reverse transcriptase domain for catalyzing genome synthesis, ribonuclease H domain for facilitating replication, and the terminal protein region for acting on the initiation of minus-strand synthesis. The HBV X region encodes HBxAg which is necessary for the prognosis of viral infection and plays a major role in oncogenic properties of HBV. Two direct repeats DR1 and DR2 in the 5´ end of the plus strand are responsible for the strand-specific DNA synthesis. En1 and En2 are the two enhancer proteins for the expression of the liver-specific viral gene. [6] MODE OF TRANSMISSION Approximately 257 million individuals are infected with HBV infection worldwide and millions of death occurred annually. [7] The virus can spread through sexual contact and parenteral and perinatal routes. Transmission through needle stick injuries is the most common in health-care workers. HBV transmission can INTRODUCTION Hepatitis B virus (HBV) can cause life-threatening liver infection such as liver cirrhosis and hepatocellular carcinoma. In 1963, Blumberg reported 1 st time about the new viral antigen from a blood sample of an Australian aborigine and named as “Australian antigen,” and later this introduced as hepatitis B surface antigen (HBsAg) protein of HBV. [1] HBV is the major public health problem worldwide. According to the WHO report, 257 million individuals are living with HBV infection. Although effective HBV vaccine available but due to lack of mass vaccination in under developed countries, hepatitis B infection increases rapidly with estimated 30 million new cases each year and 1 million die annually due to HBV disease. [2] HBV infection can transmit through blood and body fluids and most infective than HIV-related disease. [3] The present review article was undertaken to explore the pathogenesis, diagnosis, and treatment modes of hepatitis B. CLASSIFICATION HBV belongs to the Hepadnaviridae family, consisting of two genera: Orthohepadnavirus can be found in mammals and Avihepadnavirus found in birds. Due to high genetic variability in HBV, they are divided into 8 different genotypes A-H. Another three clades of HBV isolates are named as HBV chimpanzees, HBV orangutans, and HBV gibbons. [4] STRUCTURE AND GENOMIC ORGANIZATION HBV is a 42-nm enveloped, spherical, double-stranded DNA virus. It is also called as Dane particle. Other two particles are spherical ABSTRACT Hepatitis B virus (HBV) can cause life-threatening liver infection such as liver cirrhosis and hepatocellular carcinoma. In 1963, Blumberg reported 1 st time about the new viral antigen from a blood sample of an Australian aborigine and named as “Australian antigen,” and later this introduced as hepatitis B surface antigen protein of HBV. Approximately 257 million individuals are infected with HBV infection worldwide, and millions of death occurred annually. The virus can spread through sexual contact and parenteral and perinatal routes. HBV causes liver-associated diseases; it can be acute or chronic and symptomatic or asymptomatic disease. The current review provides a detailed account of HBV, its pathogenesis, diagnosis, and treatment. Key words: Diagnosis, Hepatitis B virus, infections, treatment An update on Hepatitis B virus Soumendra Nath Maity 1-3 *, S. S. Kumar 4 , R. Vijayaraghavan 1 , Rathnagiri Polavarapu 2,5,6 1 Department of Research, Saveetha Institute of Medical and Technical Sciences, Chennai, Tamil Nadu, India, 2 Department of Clinical Research Laboratory, Genomix Molecular Diagnostics Pvt. Ltd., Hyderabad, Telangana, India, 3 Department of Microbiology, Malla Reddy Institute of Medical Sciences, Hyderabad, Telangana, India, 4 Department of Physiology, Vishnu Dental College, Bhimavaram, West Godavari, Andhra Pradesh, India, 5 MNR Foundation for Research and Innovation, Sangareddy, Telangana, India, 6 Genomix CARL Pvt. Ltd., Pulivendula, Andhra Pradesh, India Address for correspondence: Soumendra Nath Maity, Department of Research, Saveetha Institute of Medical and Technical Sciences, Chennai, Tamil Nadu, India. E-mail: nath.soumendra@gmail.com Received: 10-04-2018 Revised: 25-05-2018 Accepted: 20-06-2018 ARTICLE ISSN: 2581-771X