Recombinant chimeric protein C2 containing the N-terminal region of trpE (37 kilodaltons [kDa]) and the C-terminal half (46.8 kDa) of the polypeptide encoded by ORF2 of the hepatitis E virus (HEV) genome was used for the construction of a Western blot diagnostic test for IgG and IgM antibodies to the virus (anti-HEV). (The C2 protein and the trpE protein devoid of C2 activity and used as a control for non-specific reactions were purified by recovery from sodium dodecyl sulfate-polyacrylamide gel electrophoresis [SDS-PAGE] and used for preparation of strips). Specificity of the test was proven with sera obtained from patients with acute hepatitis non-A, non-B, non-C (NANBNC) from outbreaks in different geographic regions of the world. IgG antibodies reactive to the recombinant C2 protein were detected in 93% of patients with acute hepatitis NANBNC and remained detectable in 89-100% of these patients 1-24 months after onset of jaundice. IgM antibodies were detected in 73% of patients within 26 days after onset of jaundice, in 50% 1-4 months after onset, in 6% 6-7 months after onset, and in no patients by 8 months after onset. When this test was used to identify sporadic hepatitis E cases in different regions of the world, such cases were found almost exclusively in areas where outbreaks of the disease had occurred and rarely in any other regions.