Hepatitis is an inflammatory disease of the liver, caused by infection of viruses or bacteria, etc.
A hepatologist is a doctor who specializes in the diagnosis and treatment of liver diseases.
The gastroenterologist is a doctor specializing in diseases of the digestive system including esophagus, stomach, intestines, colon and rectum, pancreas, gallbladder, bile ducts and liver.
The infectologist is a medical specialist and diseases caused by infectious agents such as bacteria, viruses, fungi and parasites.
Remember that for the proper selection of health professional that treats hepatitis you must consider the nature, severity and symptoms you are presenting.