A 32-year-old man from rural Bihar presents with jaundice, dark urine, and pale stools for 10 days. He reports consuming contaminated water 6 weeks ago. On examination, he is afebrile, icteric, with hepatomegaly but no splenomegaly. Liver function tests show ALT 2800 IU/L, AST 2200 IU/L, bilirubin 8.5 mg/dL (direct 6.2 mg/dL), albumin 3.8 g/dL, PT 12 seconds. Anti-HAV IgM is positive; anti-HEV IgM is negative. What is the most likely diagnosis?