ABSTRACT
I. GENERAL BACKGROUND Over the past 3 decades an ever-increasing number of hepatitis viruses have been described, designated by letters of the alphabet: A, B, C etc. The most important of these hepatitis viruses, A, B, and C, are major causes of morbidity and mortality worldwide. Hepatitis viruses D and E are also significant contributors to illness burden in certain parts of the world. Hepatitis F virus, obtained from the stools of a hepatitis patient, has been transmitted to primates but is probably of doubtful significance as a human pathogen (1). Hepatitis G virus, also known as hepatitis GB virus C (GB being the initials of the surgeon from whom the virus was initially isolated), is widely distributed and, in developing countries, is found in up to 18% of random outpatient blood samples (2); however its disease potential is still uncertain. Similarly, the recently described TT virus (also named after a patient, TT, from whom it was recovered) is found in 1.9% of blood donors, but its disease association is unclear (3).
