What Is It?

Hepatitis is inflammation of the liver. There are several types of hepatitis, and the disease has several causes.

In the United States today, most infectious cases of hepatitis are caused by an infection with one of the hepatitis viruses (A, B, C, D or E). An infection with one of these viruses might not cause any symptoms or might cause only a mild flulike illness. However, it also can lead to liver failure, coma and death. Hepatitis A is usually a short-term illness, while hepatitis B, hepatitis C and hepatitis D can cause long-term infections. Hepatitis E has only been found in people who have lived or traveled outside the United States.

Depending on the virus, hepatitis can be spread in a number of ways, including:

• Contact with the stool of an infected person (hepatitis A)

• Eating shellfish from waters contaminated with sewage (hepatitis A)

• Contact with the blood, vaginal fluids, semen or breast milk of an infected person (hepatitis B)

• Unprotected sex (hepatitis B and C)

• Sharing contaminated needles (hepatitis B, C and D)

Since the early 1990s, improved techniques for screening donated blood have greatly reduced the risk of catching hepatitis B or C from blood transfusions. According to the U.S. National Institutes of Health (NIH), the current risk of catching hepatitis C is 1 in 100,000 units of transfused blood.

Hepatitis has many other possible causes, including:

• Alcohol consumption at high levels, a common cause of hepatitis in the United States

• Medications, including a variety of cholesterol-lowering drugs, nitrofurantoin (Furadantin, Macrobid, Macrodantin), methyldopa (Aldomet, Amodopa), phenytoin (Dilantin and other brand names), isoniazid (Laniazid, Nydrazid), ketoconazole (Nizoral) and dantrolene (Dantrium). Hepatitis develops for unclear reasons among a small number of people who take these medications, even at prescribed doses.

• Viruses, including cytomegalovirus, Epstein-Barr virus (which causes infectious mononucleosis), herpes simplex virus, varicella virus (which causes chickenpox) and rubella (which causes German measles)

• Bacteria, including those that cause typhoid fever, syphilis, brucellosis, Legionnaires' disease and leptospirosis (though these diseases rarely cause hepatitis in the United States)

• Fungi, including histoplasmosis and candida (in people with compromised immune systems)

• Parasites, including those that cause ascariasis, toxocariasis, amebiasis, strongyloides, schistosomiasis, toxoplasmosis and malaria

• Your immune system, which can cause a condition called autoimmune hepatitis when the immune system attacks the cells of the liver