My husband has had a fever off and on for 4 weeks. The first week he was throwing up and had the runs. He has fever temps from 101.5 to 104. He will not go the ER. What could this be. The flu wouldn t last this long would it. He is 56 years old. No other health issues. He just had blood work a couple of weeks ago and they said all can back great. He is in good shape other than this issue.