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Medical Author:

Dennis Lee, MD

Dennis Lee, MD

Dr. Lee was born in Shanghai, China, and received his college and medical training in the United States. He is fluent in English and three Chinese dialects. He graduated with chemistry departmental honors from Harvey Mudd College. He was appointed president of AOA society at UCLA School of Medicine. He underwent internal medicine residency and gastroenterology fellowship training at Cedars Sinai Medical Center.

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Medical Editor:

Jay W. Marks, MD

Jay W. Marks, MD

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.

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Do You Need Vaccinations Before Traveling Abroad? 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 history. According to the U.S. Centers for Disease Control and Prevention (CDC), it's best to schedule a visit to your doctor or travel medicine clinic 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 vaccination for 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: diphtheria, tetanus, pertussis, measles, mumps, rubella, varicella, poliomyelitis, hepatitis B, Haemophilus influenzae type b, rotavirus, and pneumococcus. Read the more about traveling and required and recommended vaccinations » Top Searched Viral Hepatitis Terms: virus, vaccine, what is hepatitis A, symptoms, carriers, prognosis, causes, contagious, treated

What is viral 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 primarily attack the liver; the liver is just one of several organs that the viruses affect. When doctors speak of viral hepatitis, they usually are referring to hepatitis caused by a few specific viruses that primarily attack the liver. 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.

The liver is located in the upper right hand side of the abdomen, mostly behind the rib cage. The liver of an adult normally weighs close to three pounds. The liver performs the following vital functions:

1. 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.


2. 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 properly.


3. The liver stores many sugars, fats and vitamins until they are needed elsewhere in the body.


4. 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 hepatitis.

What are the common types of viral hepatitis?

Hepatitis A

Viral hepatitis A (HAV) accounts for about 150,000 of the 500,000-600,000 new cases of viral hepatitis that occur each year in the United States. The hepatitis caused by HAV is an acute illness (acute viral hepatitis) that never becomes chronic. At one time, hepatitis A was referred to as "infectious hepatitis" because it could be spread from person to person like other viral infections. Infection with hepatitis A virus can be spread through the ingestion of food or water, especially where unsanitary conditions allow water or food to become contaminated by human waste containing hepatitis A (the fecal-oral mode of transmission). Hepatitis A typically is spread among household members and close contacts through the passage of oral secretions (intimate kissing) or stool (poor hand washing). It also is common to have infection spread to customers in restaurants and among children and workers in day care centers if hand washing and sanitary precautions are not observed.

Hepatitis B

There are 200,000-300,000 new cases of viral hepatitis B (HBV) infection each year in the United States. Type B hepatitis was at one time referred to as "serum hepatitis," because it was thought that the only way hepatitis B virus (HBV) could spread was through blood or serum (the liquid portion of blood) containing the virus. It is now known that hepatitis B can spread by sexual contact, the transfer of blood or serum through shared needles in drug abusers, accidental needle sticks with needles contaminated with infected blood, blood transfusions, hemodialysis, and by infected mothers to their newborns. The infection also can be spread by tattooing, body piercing, and sharing razors and toothbrushes (if there is contamination with infected blood). About 6-10% of patients with hepatitis B develop chronic HBV infection (infection lasting at least six months and often years to decades) and can infect others as long as they remain infected. Patients with chronic hepatitis B infection also are at risk of developing cirrhosis, liver failure and liver cancer. It is estimated that there are 1.2 million people in the United States and 200-300 million people world-wide who suffer with chronic hepatitis B infection. article.

Hepatitis C

There are about 150,000 new cases of hepatitis C each year. Type C hepatitis was previously referred to as "non-A, non-B hepatitis," because the causative virus had not been identified, but it was known to be neither hepatitis A nor hepatitis B. The hepatitis C virus (HCV) usually is spread by shared needles among drug abusers, blood transfusion, hemodialysis, and needle sticks. Approximately 90% of transfusion-associated hepatitis is caused by hepatitis C. Transmission of the virus by sexual contact has been reported, but is considered rare. An estimated 50-70% of patients with acute hepatitis C infection develop chronic HCV infection. Patients with chronic hepatitis C infection can continue to infect others. Patients with chronic hepatitis C infection are at risk for developing cirrhosis, liver failure, and liver cancer. It is estimated that there are about 3.5 million people with chronic hepatitis C infection in the United States. For more, please see the Hepatitis C article.

Types D, E, F, and G Hepatitis

There also are viral hepatitis types D, E, F (not confirmed yet), and G. The most important of these at present is the hepatitis D virus (HDV), also known as the delta virus or agent. It is a small virus that requires concomitant infection with hepatitis B to survive. HDV cannot survive on its own because it requires a protein that the hepatitis B virus makes (the envelope protein, also called surface antigen) to enable it to infect liver cells. The ways in which hepatitis D is spread are by shared needles among drug abusers, contaminated blood, and by sexual contact, essentially the same ways as for hepatitis B.

Patients who already have chronic hepatitis B infection can acquire delta virus infection at the same time as they acquire the hepatitis B infection or, alternatively, on top of a chronic hepatitis B infection. Patients with chronic hepatitis due to hepatitis B and hepatitis D viruses develop cirrhosis (severe liver scarring) rapidly. Moreover, the combination of delta and B virus infection is very difficult to treat.