Inclusion Criteria:  Males and females ≥18 years of age. Able to read, understand, and provide signed informed consent. Willing to provide blood and stool samples. Able to communicate adequately and to comply with the requirements for the entire study. Must be willing to discontinue antibiotics 2 weeks prior to sample collection. If participating in the previously treated Lyme Disease arm, the participants must meet the following criteria: 1) Diagnosis of prior Lyme Disease supported by either an erythema migrans rash (either classic "bull's eye" or irregular) OR a CDC-positive Western blot, 2) previously treated with antibiotics for Lyme Disease, 3) remains ill six months or more after receiving preliminary treatment with antibiotics for Lyme disease (e.g., fatigue, musculoskeletal pain, or neurocognitive symptoms). If participating in the healthy volunteer arm, the participants must meet the following criteria: 1) must not have had a Lyme Disease diagnosis, 2) in generally good health  Exclusion Criteria:  1. Unwilling or unable to comply with the protocol (e.g., scheduled visits, laboratory tests, other study procedures, and study restrictions).