Describe the virology, natural history, and clinical phases of hepatitis B virus (HBV) infection. Differentiate acute from chronic hepatitis B infection based on clinical presentation and serological markers. Outline the initial clinical assessment and investigations required to evaluate patients with hepatitis B, including liver function tests, HBV serology, HBV DNA, and assessment of liver fibrosis. Interpret hepatitis B serological markers to determine infection status, infectivity, and immunity. Identify patients who require antiviral treatment based on clinical features, HBV DNA levels, alanine aminotransferase (ALT), and the presence or severity of liver fibrosis or cirrhosis. Discuss the indications, mechanisms of action, and appropriate use of first-line antiviral agents, particularly tenofovir and entecavir. Explain the management of acute hepatitis B, chronic hepatitis B, and hepatitis B in special populations, including pregnant women and patients with HIV coinfection. Recognize complications of chronic hepatitis B, including cirrhosis, hepatic decompensation, and hepatocellular carcinoma. Describe the principles of monitoring treatment response, detecting drug toxicity, and assessing disease progression. Discuss preventive strategies, including hepatitis B vaccination, prevention of mother-to-child transmission, and post-exposure prophylaxis.