A 35-year-old male official developed fever, headache, and myalgia 5 days after returning from flood relief work in a rural area, followed by oliguria, dark urine, and epistaxis, leading to hospitalization. Examination: temperature 39.6°C, marked scleral icterus, liver enlarged 2 fingerbreadths below the costal margin with tenderness, non-palpable spleen, and inguinal lymphadenopathy. Laboratory tests: total bilirubin 214 μmol/L, ALT 200 U/L, HBsAg(+), urinary protein (+++), hematuria (RBCs covering the field), Widal test 'O' 1:40, 'H' 1:320, and serum agglutination test 1:400. The diagnosis is: