Lyme disease
Of the 52 known species of "Borrelia", 20 belong to the Lyme disease group and are transmitted by ticks. Eight are known to cause Lyme disease or Borreliosis. The major "Borrelia" species causing Lyme disease are "Borrelia burgdorferi", "Borrelia afzelii", and "Borrelia garinii". All species that cause Lyme disease are referred to collectively as "B. burgdorferi" "sensu lato", while "B. burgdorferi" itself is specified as "B. burgdorferi" "sensu stricto". "B. burgdorferi" was previously believed to be the only species to cause Lyme disease in the US, but "B. bissettiae" and a new species called "B. mayonii" cause Lyme disease in the US, as well. The remaining five human pathogenic species occur only in Europe and Asia.