A patient who has been working on farms presents to the ER with a 1-week history of general malaise, skin rash, adenopathy, low-grade fever, and mild jaundice. He says he has pain in his joints and muscle. He also has a sore throat. He denies the use of any medications. Blood work reveals an elevated WBC, BUN, and creatinine. The only thing he can remember of the past is that he came into contact with milk that was probably contaminated about 2 weeks ago. He most likely has which of the following?