What Causes Reactive Arthritis?

Reactive arthritis, or Reiter's syndrome, is usually preceded by an infection caused by bacteria, such as Chlamydia trachomatis (a sexually transmitted disease) or Salmonella (a bacteria that can contaminate foods). It is important to note that the disease reactive arthritis itself is not contagious, but, rather, the bacteria that causes it. About 75 percent of persons with the tendency to develop this disease have a special gene marker called HLA-B27.