Analysis of more than 193,000 test results highlights the frequency of co-exposure and the diagnostic necessity of identifying concurrent infections requiring distinct antimicrobial treatments.
Nearly one in three individuals with antibodies against the bacterium that causes Lyme disease also tested positive for antibodies to at least one additional tick-borne pathogen, according to a study published in JAMA Network Open by researchers from Quest Diagnostics and the University of North Carolina at Chapel Hill.
The study evaluated de-identified diagnostic test results from 193,260 individuals across the US tested between January 2021 and December 2025. Investigators reported that 29.5% of patients with antibodies to Borrelia burgdorferi, the causative bacterium of Lyme disease, demonstrated co-seropositivity for other tick-borne pathogens, compared to 5.5% among those without Lyme antibodies.
The most common co-seropositivity patterns involved pathogens transmitted by the blacklegged tick, specifically Babesia microti and Anaplasma phagocytophilum. Such co-exposures can stem from bites from multiple ticks or from a single tick carrying multiple pathogens.
“The findings demonstrate that tick-borne co-exposure is a frequent clinical reality for many, particularly in Lyme disease-endemic regions like the Northeast,” says Emily I Schindler, MD, PhD, FCAP, medical director of infectious disease and immunology at Quest Diagnostics, in a release. “This research underlines the importance of comprehensive testing to bring patients the most effective treatments: because the clinical symptoms of Lyme disease, anaplasmosis and babesiosis often overlap, relying solely on single-pathogen testing can result in missed diagnoses, which can be dangerous for patients with babesiosis, which requires entirely different management than Lyme disease.”
Seasonal and Diagnostic Patterns
The dataset identified key seasonal and geographic testing concentrations, according to the release. More than 40% of diagnostic panel testing took place during the summer months of June through August, while nearly 26% occurred during the fall months of September through November. In addition, 70.6% of the tested patient cohort was located in the Northeast, aligning with established geographic distributions for the blacklegged tick vector.
According to estimates from the Centers for Disease Control and Prevention (CDC), approximately 476,000 people are diagnosed and treated for Lyme disease annually in the US. Patients infected through tick bites typically present with symptoms such as fever, headache, fatigue, and the erythema migrans rash, according to the release.
While first-line therapy for Lyme disease consists of antibiotics such as doxycycline, amoxicillin, or cefuroxime axetil, Babesia is an intraerythrocytic parasite that does not respond to these antibacterial agents. Consequently, patients with active Babesia co-infections require distinct combinations of antimicrobial regimens, according to the release.
Implications for Clinical Laboratories
“Our findings demonstrate a strikingly high rate of co-detection of antibodies against other tick-borne pathogens, particularly babesia,” says Yonghong Li, PhD, lead author and science director at Quest Diagnostics, in a release. “The sheer scale of this national dataset provides robust evidence of these co-detection patterns, making our findings highly relevant to the rapidly evolving landscape of tick-borne co-exposure.”
The authors noted that although the national dataset permitted fine-mapping of exposure trends, the reliance on serologic test results without linked clinical context represents a limitation, as positive antibody findings can indicate past exposure rather than confirmed, active acute infections, according to the release.
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