As of July 2018, 6 different infections have been recognized to be transmitted by Ixodes scapularis ticks in the United States, the most common of which is Lyme disease. The pathogen responsible for the vast majority of cases of Lyme disease in the United States is Borrelia burgdorferi. Another Lyme borrelia species, however, B. mayonii, has recently been recognized to cause Lyme disease in the North Central region of the United States. Four of these 6 infections are nationally reportable. In 2016, 36,429 confirmed or probable cases of Lyme disease were reported, in comparison with 4151 cases of Anaplasma phagocytophilum infection, 1910 cases of Babesia microti infection, and 22 cases of Powassan virus infection.