The western blacklegged tick carries the pathogens B. burgdorferi (cause of Lyme disease) and B. miyamotoi (cause of a relapsing fever (RF) illness). B. miyamotoi has been documented in Californian ticks, but human disease has yet to be detected. With a recent study showing that B. miyamotoi may survive under standard blood bank conditions, our research proposes to describe the emerging disease potential of B. miyamotoi.