People who are at risk for developing hepatitis are workers in the health care professions, people with multiple sexual partners, intravenous drug users, and hemophiliacs. Hepatitis is generally thought to be as much as ten times more common in the lower socioeconomic and poorly educated groups. About one third of all cases of hepatitis come from an unknown or unidentifiable source. This means that you don't have to be in a high risk group in order to be infected with the hepatitis virus.

Feces-contaminated water and food are the major sources of infection of Hepatitis A , and infected people can transmit it to others if they do not take strict sanitary precautions. Hepatitis A is the hepatitis strain people are most likely to encounter in the course of international travel. Up to 90% of Hepatitis B patients are men, although it can infect children. Drug users who share needles are at considerable risk. Pregnant women with hepatitis B can transmit the virus to their babies. Contaminated medical instruments, including fingerstick devices used for more than one individual, have been known to transmit the virus.

Hepatitis D occurs only in people with hepatitis B. It is not common in the US and the incidence of this hepatitis is declining rapidly overseas. Experts anticipate that it will be extremely rare in the near future. Those who recover from hepatitis B are immune to further infection from both hepatitis B and D viruses

Intravenous drug use has been the greatest risk factor for hepatitis C since the early 1980s. Although transfused blood has been tested for both hepatitis B and C since the early nineties, individuals given transfusions before then, even decades before, may still be at risk. Such individuals are urged to be tested. Most health care providers are at low risk, although the chance of infection in hospital workers who are accidentally stuck with a needle is high, ranging from 4% to 10%.

Hepatitis G accounts for about 9% of cases that cannot be diagnosed as hepatitis A through E. It also occurs in about 25% of patients with hepatitis A, 32% of those with hepatitis B, and 20% of patients with hepatitis C. Hepatitis G is detected in between 1.5% and 3.2% of blood donors and is believed to be more common than hepatitis C. From what is known of hepatitis G, its risk factors are probably similar to those of hepatitis C, although incidence among patients with multiple blood transfusions is much lower than with hepatitis C.

Autoimmune chronic hepatitis typically occurs in women between the ages of 20 and 40 who have other autoimmune diseases, including systemic lupus erythematosus, rheumatoid arthritis, Sjögren's syndrome, inflammatory bowel disease, glomerulonephritis, and hemolytic anemia. Some research indicates that the postmenopausal period may be another peak in incidence of AIH among women. About 30% of patients are men, however, and in both genders there is often no relationship to another autoimmune disease. In general, no major risk factors have been discovered for this condition.

Although heavy drinking itself is the major risk factor for alcoholic hepatitis, genetic factors may play a role in increasing a person's risk for alcoholic hepatitis. Women who abuse alcohol are at higher risk for alcoholic hepatitis and cirrhosis than are men who drink heavily. High fat diets may also increase the risk in heavy drinkers.

Severe obesity plus hypertension are the major risk factors for nonalcoholic steatohepatitis.