One in Three Lyme Patients Harbor Multiple Tick-Borne Pathogens

The study, published in JAMA Network Open, examined de-identified results from 2021 to 2025, marking the largest serology-based evaluation of multiple tick-borne pathogens to date. Researchers found that patients with Borrelia burgdorferi—the bacterium causing Lyme disease—were four times more likely to possess antibodies against secondary pathogens than those without Lyme exposure. Most co-infections involved Babesia microti and Anaplasma phagocytophilum, both transmitted by the blacklegged tick.

These findings highlight a significant diagnostic hurdle. Because symptoms of Lyme disease, anaplasmosis, and babesiosis frequently overlap, clinicians relying on single-pathogen testing risk missing co-infections. This is particularly critical for babesiosis, a parasitic infection that requires a different antimicrobial treatment regimen than standard Lyme therapies like doxycycline. Dr. Emily I. Schindler of Quest Diagnostics emphasized that comprehensive testing is necessary to ensure effective management.

Regional data underscored the severity of the issue, with 31.1% of Lyme-positive patients in the Northeast showing co-exposure, compared to significantly lower rates in the West, South, and Midwest. While the study provides a robust look at national exposure patterns, researchers noted that serological data reflects past contact with pathogens rather than strictly active, current infections. Nevertheless, the scale of the dataset confirms that as tick populations expand due to shifting environmental conditions, the likelihood of multiple simultaneous exposures is rising.