Lyme borreliosis, caused by members of the Borrelia burgdorferi sensu lato (Bbsl) complex, is the most common vector-borne disease in Europe and the USA, with over 600 000 cases estimated to occur annually in these regions since 2010.Given this impressive global burden, it is remarkable that there are still substantial diagnostic gaps for Lyme borreliosis, including the absence of reliable assays for acute infection, difficulty in differentiating past disease from current disease, and an...