Case report
A 23-year-old man with no medical history visited our hospital because his blood tested positive for HEV RNA at the time of blood donation. He had no history of smoking or drug use. His drinking was limited to occasional drinking. He had no symptoms, and laboratory tests did not show elevated hepatobiliary enzyme levels (aspartate aminotransferase, 18 IU/L; alanine aminotransferase, 8 IU/L; total bilirubin, 0.6 mg/dL); he had a normal white blood cell count of 6300/mm3 and a C-reactive protein level of 0.017 mg/dL. He tested positive for HEV immunoglobulin (Ig) A. Tests for co-infection with hepatitis B and hepatitis C were negative (Table 1). In addition, abdominal ultrasonography did not show any specific change (Figure 1). Neither the patient nor his family had a history of HEV infection. There was no obvious cause for the HEV infection, such as a history of international travel, surgery, or blood transfusion, and he had not consumed raw meat for three years. He showed no symptoms and was not diagnosed with acute HEV infection. The patient was followed up regularly in an outpatient clinic. There was no onset of clinical symptoms, and periodic outpatient blood tests showed no elevation of hepatobiliary enzymes, but HEV IgA remained positive for more than eight months. The patient has been persistently infected with HEV and followed up on an outpatient basis, but he has not developed hepatitis.