Federal surveillance now puts the number of reported babesiosis cases in the United States at 3,586 for 2023, the highest annual figure in the ten years the Centers for Disease Control and Prevention publishes on its data page, and roughly 70 percent above the 2,111 cases logged the year before.
Those numbers, posted in the CDC's babesiosis data and statistics tables, arrive in the middle of a tick season that is already among the most active in nearly a decade. They matter now for a specific and practical reason: babesiosis peaks in late summer and early fall, and the illness is caused by a parasite that infects red blood cells rather than a bacterium that produces the bullseye rash most people associate with a tick bite.
