A 20-year-old male presented with jaundice for the past 2 weeks. His liver function tests revealed serum bilirubin to be 0.9 mg/dL, SGOT/SGPT to be 1240/ 1450 IU. He was found to be positive for HBsAg and IgM anti-HEY antibodies and negative for IgM anti-c. The most likely diagnosis is -