Prevalence and implication of TT virus infection: minimal role in patients with non-A-E hepatitis in Taiwan.

TT virus (TTV) is a newly identified human DNA virus and little is known about its clinical significance. The aim of the study was to explore the prevalence of TTV infection in different risk populations and in patients with various liver diseases. Viral DNA was studied in 190 high-risk individuals, 97 household contacts, 52 patients with acute hepatitis A, 32 patients with non-A-E hepatitis including 13 fulminant hepatitis, 200 asymptomatic hepatitis B surface antigen (HBsAg) carriers, 100 patients with chronic hepatitis C, and 100 healthy adults. TTV infection was more frequent in high-risk groups (26-70%), patients with acute or fulminant non-A-E hepatitis (42-45%), and hepatitis C carriers (36%) than in healthy adults (10%) and hepatitis B carriers (15%). However, most of subjects with TTV infection alone had no or only mild hepatitis, and the same rate of TTV DNA in pre-hepatitis serum samples and constant serum TTV titers during hepatitis episodes were observed in two patients with acute non-A-E hepatitis. Phylogenetic analysis of the Taiwanese TTV isolates showed genetic heterogeneity and most (68%) isolates were TTV type 1. No particular strain was found to be associated with fulminant non-A-E hepatitis.