Chapter 15: Hepatitis B Infection

INTRODUCTION

• Hepatitis B virus (HBV) is an enveloped, double-stranded DNA virus within the family of Hepadnaviridae.

• Transmission occurs predominantly by percutaneous or mucosal contact with hepatitis B surface antigen (HBsAg)–infected blood or other bodily fluids from people with acute or chronic infection.

• The incubation period of HBV infection is 4 to 24 weeks.¹

• HBV causes both acute and chronic liver disease, with clinical symptoms ranging from asymptomatic, subclinical to fulminant hepatitis, or decompensated cirrhosis (e.g., complications of variceal bleed, ascites, spontaneous bacterial peritonitis, hepatic encephalopathy, hepatocellular carcinoma, hepatorenal syndrome, or hepatopulmonary syndrome).

• The course of HBV infection is determined by viral replication and the level of immune response in the patient.

• Despite increasing medical availability, effective antiviral treatments, and a vaccination available since 1981, hepatitis B infection remains an ongoing global health concern.

EPIDEMIOLOGY

• An estimated 2 billion people worldwide have been reported with HBV, with more than 350 million chronically infected.^1,2

• Approximately 248 million people are reported to be chronic carriers of HBsAg.^1,2

• The World Health Organization determined that approximately 600,000 people worldwide die annually from liver complications related to chronic hepatitis B (CHB).³

• Globally, HBV accounts for an estimated 30% of cases of cirrhosis and 45% to 53% of cases of hepatocellular carcinoma (HCC).^3–5

• The National Health and Nutrition Examination Survey identified approximately 704,000 adults with CHB in the United States; however, when considering foreign-born persons, estimates as high as 2.2 million have been noted.⁶

• In the United States, an estimated 3000 to 4000 people die annually from HBV-related cirrhosis. HBV-related liver cancer accounts for approximately 1000 to 1500 annual deaths.¹

• HBsAg seroprevalence and patterns of transmission are largely varied by age and geographic location (Table 15-1).^2–4

ACUTE HEPATITIS B VIRUS

• The diagnosis of acute HBV is determined by presence of serum HBsAg and immunoglobulin M (IgM) antibody to hepatitis B core antigen (anti-HBcAg).

• Acute HBV can also be diagnosed during the “window period,” in which neither HBsAg or anti-HBs are detected and IgM anti-HBc can be positive.

• Progression from acute infection to CHB is estimated to be less than 5%.⁷

• Treatment is mainly supportive. However, ...