Reactive arthritis is associated with the family of spondylitis diseases. There is excellent information about reactive arthritis at the Spondylitis Association of America's website. When you get there, go to the about spondylitis section at the top. Then you will seen where to click for information on Reactive Arthritis. The following excerpt from their site should answer some of your questions:
"ReA usually develops 2-4 weeks after the infection. A tendency exists for more severe and long-term disease in patients who do test positive for HLA-B27 as well as those who have a family history of the disease.
Reactive Arthritis typically follows a limited course, where symptoms subsiding in 3-12 months. However, the condition has a tendency to recur. about 15-20% of people with ReA develop a chronic, and sometimes severe, arthritis or spondylitis."