The diagnosis of type A hepatitis is performed mainly by incidence of sporadic type A hepatitis is still at problematic levels in this country. 1 immunoglobulin M (IgM) anti-hepatitis A antibody assay, but it has not been established whether there is a correlation HAV is a positively stranded RNA virus of approximately 7,500 nucleotides. It is composed of a 5 non-translated re-between changes in viremia and the clinical course of type A hepatitis. We examined hepatitis A virus (HAV) RNA in the gion (NTR), structural protein regions, nonstructural protein regions, and a 3 NTR. 2 By examining the nucleotide se-sera from type A and non-A, non-B, non-C acute hepatitis and analyzed the relation of HAV viremia with alanine aminotrans-quences of structural protein viral protein 1 and nonstructural protein 2a regions, HAV can be classified into at least 7 ferase (ALT) and IgM-HA levels. Two hundred sera from 38 patients with type A acute hepatitis and 20 patients with genotypes. 3 5-NTR and 3-NTR of HAV are approximately 735 and 63 nucleotides in length, respectively, and these non-A, non-B, non-C acute hepatitis were examined for the presence of HAV RNA. HAV RNA was detected by nested regions have high homology among the various strains so far reported. 2,4,5 reverse transcription-polymerase chain reaction (RT-PCR) with primers located at the 5 non-translated region of HAV. Although HAV is extensively studied virologically, a correlation between viral characteristics and clinical status has not HAV RNA was detected in 35 of 38 (92%) type A hepatitis patients and in 60 of 156 (38%) serum samples. In contrast, been established. Thus, viremia in type A hepatitis still needs to be examined to better understand the disease. So far, diag-it was detected in none of 44 serum specimens from 20 non-A, non-B, non-C acute hepatitis patients. In type A hepatitis, nosis of type A hepatitis has been based on serological markers, especially by detecting IgM anti-HA antibody (IgM-HA), 6 the mean ALT level in HAV RNA positive specimens was 1,481 { 2,042 (range, 20-10,370) IU/L and that in HAV RNA and the relation between the continuity of viremia and the clinical conditions has not yet been well delineated. We de-negative specimens 186 { 330 (range, 8-1,698). The positivity of HAV RNA was correlated with the level of transaminase veloped a sensitive detection method of HAV RNA by nested reverse transcription-polymerase chain reaction (RT-PCR) at at the time of sample collection. The mean duration from the onset of symptoms to disappearance of HAV RNA was 18 { 5-NTR with high homology among the various strains of HAV; we also examined HAV RNA in sera to determine the 14 days. The mean titer of IgM-HA in HAV RNA positive cases was 5.0 { 1.4, in negative cases 5.7 { 1.1, with no possible correlation of HAV viremia and clinical status. statistical difference. Our results indicate that HAV RNA in serum is detectable in the majority of type A hepatitis cases PATIENTS AND METHODS in their early convalescent phase by nested RT-PCR. (HEPA-Patients