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.
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