Is Lyme Disease More Common Now — Or Not?

Lyme disease, caused by the Borrelia burgdorferi spirochete, has a U.S. distribution concentrated in the Northeast, mid-Atlantic, and upper Midwest. Annual disease incidence as reported by CDC has increased 1.7-fold between 2017–2019 and 2022. Researchers sought to determine whether this stated increase represents new infections or is an artifact of changes in reporting guidelines. Before 2017, reportable disease was based on clinical history plus laboratory testing for antibodies to B. burgdorferi. Since then, testing has become more specific; thus, history and clinical presentation have been largely abandoned as criteria for reporting to the CDC.

Based solely on laboratory testing results, reports of Lyme disease have approximately doubled…