Mary D. Nettleman, MD, MS, MACP is the Chair of the Department of Medicine at Michigan State University. She is a graduate of Vanderbilt Medical School, and completed her residency in Internal Medicine and a fellowship in Infectious Diseases at Indiana University.
Hepatitis B is an infectious hepatitis caused by the hepatitis B virus (HBV).
This infection has two possible phases; 1) acute and 2) chronic.
Acute hepatitis B refers to newly acquired infections. Affected
symptoms approximately 1 to 4 months after exposure to the virus. In most people
with acute hepatitis, symptoms resolve over weeks to months and they are cured
of the infection. However, a small number of people develop a very severe,
life-threatening form of acute hepatitis called fulminant hepatitis.
Chronic hepatitis B is an infection with HBV that lasts longer than 6
months. Once the infection becomes chronic, it may never go away completely.
Approximately 90% to 95% of infected adults are able to fight off the virus so
their infection is cured. Only about 5% to 10% of adults infected with HBV go on to
develop chronic infection. Children are at much higher risk for chronic
infection. Up to 90% of infected young children will fail to clear the virus from
their bodies and go on to develop chronic infection.
About two-thirds of people with chronic HBV infection are chronic carriers.
These people do not develop symptoms, even though they harbor the virus and can
transmit it to other people. The remaining one third develop "active" hepatitis,
a disease of the liver that can be very serious.
The liver is an important organ that filters toxins out of the blood,
stores energy for later use, helps with digestion, and makes substances that
fight infections and control bleeding.
The liver has an incredible ability to heal itself, but long-term
inflammation caused by HBV can result in permanent damage.
Scarring of the liver is called cirrhosis, a condition traditionally
associated with alcoholism but one that is also caused by chronic active
hepatitis B infection. When this occurs, the liver can no longer carry out its
normal functions and may fail completely. The only treatment for liver failure
is liver transplant.
Chronic hepatitis B also can lead to a type of liver cancer known as
Any of these conditions can be fatal. About 15% to 25% percent of people with
chronic hepatitis B die of liver disease.
Hepatitis B is the most common serious liver infection in the world.
Worldwide, about 350 million people are chronic carriers of HBV, of whom, more
than 620,000 die from liver-related disease each year.
In the United States, hepatitis B is largely a disease of young adults aged
20-50 years. About 800,000 to 1.4 million Americans are chronic hepatitis B
virus carriers, and
the disease causes about 3, 000 deaths each year.
The good news is that infection with HBV is usually preventable because
there is an effective vaccine. Use of the vaccine has resulted in an 82%
decrease in the number of new infections reported in the United States each
Figure 1: Estimated and reported cases of hepatitis B in the United States. Rates have fallen significantly since 1991 when routine vaccination of children was started.
Image courtesy of the CDC.