Rat-bite fever (RBF) is a rarely diagnosed, systemic illness caused by infection with Streptobacillus moniliformis, Streptobacillus notomytis, or Spirillum minus S. moniliformis, which causes most cases in the United States. Spirillum minus, primarily in Asia, is also known as Sodoku disease, although it may occur worldwide. S. notomytis infections are rarely reported.