Dr. Charles "Pat" Davis, MD, PhD, is a board certified Emergency Medicine doctor who currently practices as a consultant and staff member for hospitals. He has a PhD in Microbiology (UT at Austin), and the MD (Univ. Texas Medical Branch, Galveston). He is a Clinical Professor (retired) in the Division of Emergency Medicine, UT Health Science Center at San Antonio, and has been the Chief of Emergency Medicine at UT Medical Branch and at UTHSCSA with over 250 publications.
Jay W. Marks, MD, is a board-certified internist and gastroenterologist. He graduated from Yale University School of Medicine and trained in internal medicine and gastroenterology at UCLA/Cedars-Sinai Medical Center in Los Angeles.
Many illnesses and conditions can cause inflammation of the liver (hepatitis), but certain viruses cause about half of all hepatitis in people.
Viruses that primarily attack the liver are called hepatitis viruses. There are several types of hepatitis viruses including types
C, D, E, and possibly G. Types A, B, and C are the most common.
Those at risk for viral hepatitis include workers in the health care profession, people with multiple sexual partners, intravenous drug abusers, and
hemophiliacs. Blood transfusion is a rare cause of viral hepatitis.
All hepatitis viruses can cause acute hepatitis.
Viral hepatitis types B and C can cause chronic hepatitis.
Hepatitis means inflammation of the liver. Many illnesses and conditions can cause inflammation of the liver, for example, drugs, alcohol, chemicals, and autoimmune diseases. Many viruses, for example, the virus of mononucleosis and the cytomegalovirus can inflame the liver. Most viruses, however, do not attack primarily the liver; the liver is just one of several organs that the viruses affect. When doctors speak of viral hepatitis, they are using the definition that means hepatitis caused by a few specific viruses that primarily attack the liver and are responsible for about half of all human hepatitis. There are several hepatitis viruses; they have been named types A, B, C, D, E, F (not confirmed), and G. As our knowledge of hepatitis viruses grows, it is likely that this alphabetical list will become longer. The most common hepatitis viruses are types A, B, and C. Reference to the hepatitis viruses often occurs in an abbreviated form. (For example, HAV, HBV, HCV represent hepatitis viruses A, B, and C, respectively.)
Hepatitis viruses replicate (multiply) in the liver cells. Newly-produced viruses are released into the blood stream where they can be spread to other organs or to other persons exposed to the infected blood.
The liver helps purify the blood by changing harmful chemicals into harmless
ones. The source of these chemicals can be external, such as medications or
alcohol, or internal, such as ammonia or bilirubin. Typically, these harmful
chemicals are broken down into smaller chemicals or attached to other chemicals
that then are eliminated from the body in the urine or stool.
The liver produces many important substances, especially proteins that are
necessary for good health. For example, it produces albumin, the protein
building block of the body, as well as the proteins that cause blood to clot
The liver stores many sugars, fats and vitamins until they are needed
elsewhere in the body.
The liver builds smaller chemicals into larger, more complicated chemicals
that are needed elsewhere in the body. An example of this type of function is
the manufacture of cholesterol.
When the liver is inflamed, it does not perform these functions well, which brings about many of the symptoms, signs, and problems associated with any type of hepatitis. Each viral type has both articles and books describing the details of infection with that specific virus. This article is designed to give the reader an overview of the predominant viruses that causes viral hepatitis and should help the reader choose the subject(s) for more in depth information.
Medical Author: Melissa Conrad Stöppler, MD
Medical Editor: William C. Shiel, Jr, MD, FACP, FACR
Travelers to other countries often face health issues
they wouldn't ordinarily experience at home. To minimize your risks of becoming
seriously ill when traveling abroad, you should find out in advance whether any
specific immunizations may be recommended for travel to the region of the world
you'll be visiting. It's also a good time to review your own immunization
According to the U.S. Centers for Disease Control and Prevention(CDC), it's best to
schedule a visit to your doctor or travel medicineclinic 4-6 weeks before an
international trip. Since your body needs time to build up immunity after
receiving a vaccine and many vaccines are given in a series over time,
getting an early start on your immunizations is the best way to protect
yourself. Even if you are making a last-minute trip or plan to leave in less
than four weeks, you should still check with your doctor to see if any vaccines
or preventive medications might be recommended.
The CDC divides travel vaccinations into three categories: routine,
recommended, and required. The only vaccine classified as "required" by
International Health Regulations is the yellow fever vaccinationfor travel to
certain countries in sub-Saharan Africa and tropical South America.
"Routine" vaccinations are those that are normally
administered, usually during childhood, in the United States. These include immunizations against: