What Is Hepatitis B?

There are different types of hepatitis viruses, including hepatitis A, B, C, D, E, and G.
Hepatitis is a disease of the liver. Hepa comes from the Greek word for liver, and itis is Latin for “inflammation.” Thus, hepatitis is “inflammation of the liver.” When you have hepatitis, your liver doesn’t work normally. In rare cases, the liver can fail altogether. Your liver plays a key role in keeping you healthy, purifying your blood, and supplying chemicals that your body needs. Liver disease can have serious short- and long-term effects on your health.

Hepatitis is not a single disease. Rather, it is inflammation of the liver that can result from various causes. Most forms of hepatitis come from infection with a virus. There are different types of hepatitis viruses, including hepatitis A, B, C, D, E, and G. This article deals specifically with hepatitis B. The Centers for Disease Control and Prevention (CDC) estimated that 21,600 people in the United States contracted hepatitis B in 2018 (the last year for which data is available). Between two thousand and four thousand people die from hepatitis B each year in the United States. Today, between 800,000 and 1.9 million Americans have the virus. The Public Health Agency of Canada estimates that between 0.7 and 0.9 percent of the Canadian population is chronically infected with hepatitis B. According to data from the World Health Organization (WHO), as of 2019 approximately 820,000 people die as a result of hepatitis B worldwide every year.

Microscope image of Hepatitis B virus
Microscope image of Hepatitis B virus.
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CDC/Dr. Erskine Palmer

Hepatitis B is carried in the blood and other body fluids and is caused by the hepatitis B virus (HBV). It is most often passed from one person to another in semen or blood as a result of having unprotected sex or from sharing a hypodermic needle. It may also be contracted from blood transfusions, although this is rare. It is also possible to pass on HBV via saliva, tears, or sweat, if there is direct contact with a cut or scratch. However, this type of transmission is less likely because the concentration of the virus is lower in these fluids.