Relationship of TT virus infection with prevalence of hepatitis C virus infection and elevated alanine aminotransferase levels.

A novel DNA virus, TT virus (TTV), was identified in a Japanese patient with posttransfusion hepatitis. The epidemiology and etiological role of this virus have not been elucidated. We investigated the epidemiology of TTV infection in hepatitis C virus (HCV) high endemic and low endemic areas, R town and M town, respectively. The seroprevalence, potential risk factors, and laboratory features of TTV in relation to those of HCV were analyzed. TTV DNA was detected using a seminested polymerase chain reaction and the TTV genotypes were determined by a direct sequencing method. TTV DNA was detected in 16.1% of the subjects in R town and 17.5% of those in M town. The TTV DNA positivity rates of the 2 areas did not differ significantly. A history of blood transfusion was not a specific risk factor for TTV infection. The mean serum alanine aminotransferase (ALT) level of the anti-HCV-positive subjects was significantly higher than that of the TTV DNA-positive subjects, most of whom had normal ALT levels. The TTV genotype distributions of these 2 distinct areas differed. These results suggest that TTV infection is widespread with a geographical genotypic distribution independent of HCV infection and that the ALT abnormalities are not attributable to TTV but to HCV infection in the general population.