Hepatitis A and Hepatitis B
Hepatitis A and Hepatitis B
Electron micrograph of hepatitis A virus (HAV)
Symptoms and Causative Agent
Hepatitis is a general term for inflammation of the liver, which may result from infectious or non-infectious causes. Viruses responsible for many cases of infectious hepatitis include hepatitis A, hepatitis B, hepatitis C, hepatitis D, and hepatitis E. Hepatitis A and B are the only hepatitis viruses for which vaccines are currently available in the United States (although immunity for hepatitis B also confers immunity for hepatitis D--sometimes known as delta hepatitis).
The hepatitis B virus (HBV) is a partly double-stranded DNA virus in the hepadnavirus family. The hepatitis A virus (HAV) is a single-stranded RNA virus in the picornavirus family. Both viruses, though they are structurally unrelated to one another, infect and replicate primarily in liver cells.
The symptoms of acute hepatitis A infection are identical to those of hepatitis B infection. Early symptoms are headache, nausea, vomiting, abdominal pain, fever, rash, body aches and pains, and dark colored urine. Following this phase, jaundice (yellow-colored skin and whites of the eyes), light stools, and liver pain may appear.
The hepatitis B virus is spread via contact with infectious body fluids (namely, blood, saliva, and semen). It can be spread sexually, or through sharing of injection drug use equipment, needle sticks, birth to an infected mother, contact with open sores or wounds of an infected person, and sharing of razors or toothbrushes with an infected person. While saliva can serve as a means of transmission in bites, it is not likely that kissing is a viable means of transmitting the virus.
The fecal-oral route is the main transmission pathway for the hepatitis A virus. This may occur through person-to-person contact or by eating or drinking contaminated food or water. HAV is not known to be spread via saliva. In very rare cases it has been spread via contaminated blood transfusions.
Both viruses are extremely hardy and can remain infectious on surfaces for more than seven days at room temperature, although this is unlikely to account for infection transmission in most cases.
Treatment and Care
No specific treatments exist for acute hepatitis A and B infections. Rather, they are treated with supportive care, such as rest, fluid management, and pain and fever relief.
See below for a discussion of treatment for chronic hepatitis B infection.
Both hepatitis A and hepatitis B infection can have immediate, deadly consequences. Approximately 1% of people with acute HBV infections will suffer fulminant hepatitis, or acute liver failure. HAV infection may also, though less commonly than HBV infection, lead to fulminant hepatitis. Up to 90% of patients with fulminant hepatitis will die.
Up to 95% of adults infected with acute HBV infection recover and do not become chronically (permanently) infected, although they can infect other people during the acute phase via transmission of body secretions. The others become chronically infected—and able to infect others for a much longer time (in some cases for many years)—and are at risk for serious liver disease. The picture is different for children: infants and children who become infected with hepatitis B are much more likely than adults to become chronically infected and hence to develop serious, late complications.
Chronic infection with HBV may lead to cirrhosis, liver failure, and liver cancer. HAV infection does not lead to chronic infection or chronic liver disease.
Treatment for patients with chronic HBV infection may include interferon therapy, which reduces or eliminates the virus in some patients. Interferon blocks viral replication and enhances the body’s immune response to infected cells. Because interferon is an injectable medicine and has some potentially serious side effects, some patients may be advised to delay or avoid interferon treatment or to use one of the several oral medicines such as lamivudine, adefovir or entecavir. Treatment is always administered and monitored by a clinician familiar with viral hepatitis.
Available Vaccines and Vaccination Campaigns
Hepatitis B Vaccines
The FDA has licensed several hepatitis B vaccines for use in the United States, including several combination vaccines. It has been part of the routine childhood immunization schedule since 1994. Some parents object to vaccinating their newborns against a disease they mistakenly think is spread only via sexual contact and IV drug use. However, newborns and young children are at risk for hepatitis B infection: apart from maternal transmission of hepatitis B to a newborn, hepatitis B transmission has been reported in school and daycare settings among children. The vaccine contains no live virus and is safe even for people with reduced immune function.
Following are the general recommendation for hepatitis B vaccination:
Hepatitis B vaccination is recommended for all children, starting at birth in a three-dose series spread over many months. Additionally, all children and adolescents under age 19 who have not been vaccinated are recommended to receive the vaccine, as are adult populations at risk of HBV infection.
Hepatitis A Vaccines
Several vaccines for hepatitis A are available in the United States, including several combination vaccines. It has been part of the routine childhood immunization schedule since 1994. Hepatitis vaccination is recommended at age 1, with a booster shot several months later. For those people who have not had hepatitis A and have not already been vaccinated, travel to developing countries can be a trigger for pre-departure hepatitis A vaccine. It is important to allow at least two weeks before departure for vaccination. The benefits of a single administration of vaccine should last for several months, but getting a second dose will confer much longer term immunity. The vaccine contains no live virus and is safe even for people with reduced immune function.
Following are the general recommendations for hepatitis A vaccination:
Hepatitis A vaccination is recommended for all children at age 1 year, for persons who are at increased risk for infection, for persons who are at increased risk for complications from hepatitis A, and for any person wishing to obtain immunity.
Hepatitis E Vaccines
A recombinant hepatitis E vaccine was licensed in China in 2011 for use in people ages 16-65 years old. It is recommended for those at high risk of hepatitis E infection.
Centers for Disease Control and Prevention. Epidemiology and Prevention of Vaccine-Preventable Diseases. Atkinson W, Wolfe S, Hamborsky J, eds. 13th ed. Washington, DC: Public Health Foundation, 2015. http://www.cdc.gov/vaccines/pubs/pinkbook/downloads/hepa.pdf (468 KB). Accessed 2/5/2016.
Centers for Disease Control and Prevention. Epidemiology and Prevention of Vaccine-Preventable Diseases. Atkinson W, Wolfe S, Hamborsky J, eds. 13th ed. Washington DC: Public Health Foundation, 2015. http://www.cdc.gov/vaccines/pubs/pinkbook/downloads/hepb.pdf (1.1 MB). Accessed 2/5/2016.
Feigin RD, Cherry JD, Demmler GJ, Kaplan SL. Textbook of Pediatric Infectious Diseases, 5th ed., vol 2. Philadelphia: Saunders, 2004.
Immunization Action Coalition. Unusual cases of hepatitis B virus transmission. http://www.immunize.org/catg.d/p2100nrs.pdf Accessed 2/5/2016.
Plotkin SA, Orenstein WA, Offit PA. Vaccines, 5th ed. Philadelphia: Saunders, 2008.
World Health Organization. Hepatitis E Vaccine: WHO Position Paper, May 2015. http://www.who.int/wer/2015/wer9018.pdf?ua=1 Accessed 2/25/2016.
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Last update 25 February 2016
Timeline Entry: 1965
Hepatitis B: The Australia Antigen
American physician and researcher Baruch Blumberg, MD, PhD (1925-2011), was interested in how genes could influence susceptibility to disease. He traveled the world collecting and studying blood samples from different populations. With a new lab technique, he matched a protein found in the blood of an Australian aborigine with an antibody in the blood of a hemophiliac from the United States. He called the protein the "Australia antigen."
Blumberg and others were able to connect the presence of the antigen with hepatitis B infection. The Australia antigen proved to be the hepatitis B virus (HBV) surface protein. Later they related HBV infection to liver cancer.
The Australia antigen circulates in the blood of a previously infected person not only as part of HBV, but also as a small, independent particle. The discovery of the Australia antigen had an important effect on the study of hepatitis B, in large part because HBV cannot be cultivated in the lab. The Australia antigen could, therefore, serve as a model for the virus as a whole. Moreover, the Australia antigen provided a source for antigen for the vaccine.
Blumberg would win the Nobel Prize in Medicine in 1976 for his work on hepatitis B.See this item in the timeline
Timeline Entry: 7/23/1986
Hepatitis B: Recombinant Vaccine Licensed
The FDA licensed Merck’s Recombivax HB. This hepatitis B vaccine was the first human vaccine produced by recombinant DNA methods.
A challenge in creating the vaccine involved avoiding the use of human blood products, as did Maurice Hilleman’s first hepatitis B vaccine. Therefore, Merck used an enzyme to remove the virus’s surface protein (HBsAg, the Australia antigen). Researchers inserted the code for the antigen into yeast cells, which produced more of the surface protein. The yeast-derived surface protein produced immunity to the hepatitis B virus.See this item in the timeline
Hepatitis refers to diseases of the __________.
__________ mainly spread via the fecal-oral route.
- Hepatitis A and B are
- Hepatitis B is
- Hepatitis A is
- None of the above
True or false? Hepatitis B infection can lead to chronic disease.