BACKGROUND: The duration of viremia during hepatitis E virus (HEV) infection has rarely been reported. This study was undertaken to detect HEV RNA in sera of patients with hepatitis E and to understand the process of HEV infection more thoroughly. METHODS: HEV RNA was detected in the serum samples of hospitalized patients with acute hepatitis E by reverse transcriptase-nested polymerase chain reaction (RT- nPCR) using two pairs of primers from open reading frame (ORF) 1 of the HEV genome. RESULTS: The serum samples from 44 (70%) of 62 patients were positive for HEV RNA. Thirty-two of these patients, with 288 serial serum specimens, were followed up for the whole process, and 24 patients (75%) were positive for HEV RNA. The positive rates declined with the course of the disease, serum HEV RNA persisting for 20.6 days on average after onset of illness. Serum HEV RNA remained positive in 36 (81.8%) of the 44 patients at the time their alanine aminotransferase (ALT) began to decrease. There was no difference in HEV RNA positivity between serum with high levels of HEV antibody (peak P/N ratio ≥ 4.0) and that with low levels (peak P/N ratio <4.0), with 25 out of 35 and 19 out of 27 (71.4% vs. 70.4%, P>0.05), respectively. CONCLUSIONS: There is a relatively long period of HEV viremia in patients with hepatitis E. The proportion of HEV viremia and its duration are not directly related to serum ALT values or HEV antibody levels. This study was undertaken to detect HEV RNA in sera of patients with hepatitis E and to understand the process of HEV infection more thoroughly. METHODS: HEV RNA was detected in the serum samples of hospitalized patients with acute hepatitis E by reverse transcriptase-nested polymerase chain reaction (RT-nPCR) using two pairs of primers from open reading frame (ORF) 1 of the HEV genome. (70%) of 62 patients were positive for HEV RNA. Thirty-two of these patients, with 288 serial serum specimens, were followed up for the whole process, and 24 patients (75%) were positive for HEV RNA. The positive rates declined with the course of the disease, serum HEV RNA persisting for 20.6 days on average after onset of illness. Serum HEV RNA remained positive in 36 (81.8%) of the 44 patients at the time their alanine aminotransferase (ALT) began to decrease. Ther e was no difference in HEV RNA positivity between serum with high levels of HEV antibody (peak P / N ratio ≥ 4.0) and that with low levels (peak P / N ratio <4.0) with 25 out of 35 and 19 out of 27 (71.4% vs. 70.4%, P> 0.05), respectively. CONCLUSIONS: There is a relatively long period of HEV viremia in patients with hepatitis E. The proportion of HEV viremia and its duration are not directly related to serum ALT values ​​or HEV antibody levels.