Hepatitis B

What is hepatitis B?

Hepatitis B is a potentially life-threatening liver infection caused by the hepatitis B virus (HBV). Hepatitis B infection can be either acute or chronic. Acute hepatitis B infection is short term, lasting a few weeks. Chronic hepatitis B infection is lifelong and can cause illnesses like cirrhosis and liver cancer.1



Hepatitis B Infection Can Range From an Acute Illness Lasting a Few Weeks to a Chronic, Lifelong Illness

Lasting a few weeks

Lifelong illness

What is the prevalence of hepatitis B in the United States?

Acute hepatitis B: In 2018, a total of 3,322 cases of acute HBV were reported to CDC, for an overall incidence rate of 1.0 cases per 100,000 population.1,2 After adjusting for under-ascertainment and under-reporting, an estimated 21,600 acute hepatitis B cases occurred in 2018.1

Chronic hepatitis B: In 2016, an estimated 862,000 people were chronically infected with HBV.1

What are the signs and symptoms of acute hepatitis B?

Hepatitis B doesn’t always cause symptoms and the presence of symptoms varies with age. Most children <5 years of age and newly infected immunosuppressed adults are generally asymptomatic, whereas 30%–50% of people age ≥5 years have signs and symptoms.2

For those who do experience symptoms; however, acute hepatitis B may be manifested as2:

  • Fever
  • Fatigue
  • Loss of appetite
  • Nausea
  • Vomiting
  • Abdominal pain
  • Dark urine
  • Clay-colored stool
  • Joint pain
  • Jaundice

Who is at risk for chronic hepatitis B?

The likelihood that infection becomes chronic depends upon the age at which a person becomes infected.1

The Likelihood That Hepatitis B Infection Becomes Chronic Depends On the Age at Which a Person Becomes Infected

Acute HBV progresses to chronic HBV in approximately 40% of hemodialysis patients and up to 20% of patients with immune deficiencies.3

How serious is hepatitis B?

Although the consequences of acute HBV infection can be severe, most of the serious complications associated with HBV infection are due to chronic infection.3

Chronic infection is responsible for most HBV-related morbidity and mortality, including:

  • Cirrhosis
  • Liver failure
  • Hepatocellular carcinoma

Approximately 25% of persons who become chronically infected during childhood and 15% of those who become chronically infected after childhood will die prematurely from cirrhosis or liver cancer.3

How is hepatitis B transmitted?

Hepatitis B transmission occurs through activities that involve percutaneous or mucosal contact with infectious blood or body fluids (eg, semen and saliva), including1,2:

  • Sex with an infected partner
  • Injection-drug use that involves sharing needles, syringes, or drug-preparation equipment
  • Birth (spread from an infected mother to her baby)
  • Contact with blood from or open sores on an infected person
  • Exposures to needle sticks or sharp instruments
  • Sharing certain items with an infected person that can break the skin or mucous membranes (eg, razors, toothbrushes, and glucose monitoring equipment), potentially resulting in exposure to blood

How does hepatitis B transmission NOT occur?

Unlikely modes of hepatitis B transmission include1,3:

  • Kissing, hugging, holding hands
  • Sharing meals, bowls, or utensils with someone who is infected
  • Tears
  • Sweat
  • Urine
  • Stool
  • Droplet nuclei (eg, airborne transmission through coughing or sneezing)
  • Breastfeeding
  • Food
  • Water

How is hepatitis B diagnosed?

Diagnosis is based on clinical, laboratory, and epidemiologic findings. HBV infection cannot be differentiated on the basis of clinical symptoms alone, and definitive diagnosis depends on the results of serologic testing. Serologic markers of HBV infection vary depending on whether the infection is acute or chronic.3

How is hepatitis B treated?

People with acute infection are provided supportive treatment depending on their symptoms. For people with chronic infection, several antiviral medications are available; these patients require linkage to care with regular monitoring to prevent liver damage and/or hepatocellular carcinoma. The American Association for the Study of Liver Diseases (AASLD) has published practice guidelines for the treatment of chronic hepatitis.2

CDC Disease Information

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CDC=Centers for Disease Control and Prevention; HBV=hepatitis B virus.



  1. Hepatitis B fact sheet. World Health Organization (WHO). http://www.who.int/news-room/fact-sheets/detail/hepatitis-b. Updated July 18, 2019. Accessed October 3, 2019.


  1. Hepatitis B questions and answers for the public. Centers for Disease Control and Prevention. https://www.cdc.gov/hepatitis/hbv/bfaq.htm. Updated September 10, 2019. Accessed October 3, 2019.


  1. Centers for Disease Control and Prevention. Hepatitis B. In: Hamborsky J, Kroger A, Wolfe S, eds. Epidemiology and Prevention of Vaccine-Preventable Diseases. 13th ed. Washington, DC: Public Health Foundation; 2015:149–174. http://www.cdc.gov/vaccines/pubs/pinkbook/index.html. Accessed August 9, 2018.


  1. Hepatitis B basic information. US Department of Health & Human Services. https://www.hhs.gov/hepatitis/learn-about-viral-hepatitis/hepatitis-b-basics/index.html. Updated January 30, 2019. Accessed October 3, 2019.

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Merck does not review or control the content at the site to which this link connects. Merck makes no representation with respect to the content of any non-Merck site.



  1. Centers for Disease Control and Prevention. Hepatitis B questions and answers for the public. https://www.cdc.gov/hepatitis/hbv/bfaq.htm Updated July 28, 2020. Accessed September 20, 2021.


  1. Centers for Disease Control and Prevention. Hepatitis B questions and answers for health professionals. https://www.cdc.gov/hepatitis/hbv/hbvfaq.htm#a2 Updated July 28, 2020. Accessed September 29, 2021.


  1. Centers for Disease Control and Prevention. Epidemiology and prevention of vaccine-preventable diseases. In: Hall E, Wodi AP, Hamborsky J, et al, eds. 14th ed. Washington, D.C. Public Health Foundation, 2021: 143–164. http://www.cdc.gov/vaccines/pubs/pinkbook/index.html.

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