Residual clinical specimens [whole blood (EDTA), synovial fluid, cerebrospinal fluid (CSF), and tissue] submitted to Mayo Clinic from health care providers nationwide for patients suspected of having a tickborne illness [i.e. testing by either Tick Borne Pathogen PCR Panel (Babesia, Ehrlichia/Anaplasma) or Lyme (Borrelia burgdorferi sensu lato) PCR] and the accompanying nucleic acid extract were stored at 4°C or −70°C, de-identified and shipped to the Minnesota Department of Health (MDH). Synovial fluid, CSF, and tissue specimens were originally submitted for Lyme PCR, whereas blood specimens were submitted for either Tick Borne Pathogen PCR Panel or Lyme PCR. Aliquots of each clinical specimen were prepared, frozen at −70°C, and shipped to the Centers for Disease Control and Prevention, Fort Collins, CO. Associated patient information included specimen type, originating state of the ordering provider, patient age, and sex. As travel history of patients was not available, the state of the ordering provider does not necessarily correlate to the patient’s state of residence or exposure. Analysis of de-identified specimens was approved by the Institutional Review Board at Mayo Clinic (Protocol ID: 14-001148). Review at MDH and CDC determined the protocol to be non-human subjects research.