The incubation period is usually 1-2 weeks, and the duration of the illness is about 3-4 weeks. Symptoms include:Poor appetiteHeadachesGeneralized aches and painsFever as high as 104 degrees FarenheitLethargyDiarrheaChest congestion develops in many people, and abdominal pain and discomfort are common. The fever becomes constant. Improvement occurs in the third and fourth week in those without complications. About 10% of people have recurrent symptoms after feeling better for one to two weeks. Relapses are actually more common in individuals treated with antibiotics.