Nearly one in three people who tested positive for antibodies to the bacterium that causes Lyme disease also had antibodies to at least one other tick-borne pathogen, according to a study published in JAMA Network Open. Researchers from Quest Diagnostics and the University of North Carolina at Chapel Hill found the overlap in 29.5% of Lyme-positive patients, compared with 5.5% of people without Lyme antibodies.
The finding matters now because tick season is not over. Nearly 26% of the testing in the study occurred in September through November, and the most common co-exposures involved Babesia and Anaplasma, which are spread by the same blacklegged ticks that carry Lyme disease.
One important limitation comes first. Antibodies show that the immune system encountered a germ at some point. They do not prove a current infection, and the study included only people whose clinicians ordered tick-borne disease testing, not the general population.
Inside the National Lab Data
The researchers analyzed de-identified test results from 193,260 people tested between January 2021 and December 2025, according to a Quest Diagnostics release. The average patient was 51, and 92% were adults.
Across everyone tested, 5.0% had antibodies to Borrelia burgdorferi, the Lyme bacterium. Another 3.4% had antibodies to Babesia microti, a malaria-like parasite, 3.1% to Anaplasma phagocytophilum, and 1.0% to Ehrlichia species. After adjusting for other factors, people with Lyme antibodies were 4.5 times as likely to have antibodies to another tick-borne pathogen, CIDRAP reported.
Geography made a large difference. About 71% of patients lived in the Northeast, where 31.1% of Lyme-positive patients had another antibody, compared with 16.6% in the Midwest, 16.0% in the South, and 13.6% in the West. Babesia was the most common co-detection, reaching 18.5% of Lyme-positive patients in the Northeast. That points to Northeastern families as the most likely to face overlapping exposures.
One result was less expected. People with Lyme antibodies were also more likely to have antibodies to Ehrlichia, which is usually spread by the lone star tick rather than the blacklegged tick. The authors suggested possible explanations, including exposure to several tick species over time, test cross-reactivity with Anaplasma, or an Ehrlichia species also carried by blacklegged ticks, but the study could not determine which is correct.
"The findings demonstrate that tick-borne co-exposure is a frequent clinical reality for many, particularly in Lyme disease-endemic regions like the Northeast," said Dr. Emily I. Schindler, medical director for infectious disease and immunology at Quest Diagnostics.
Antibodies Are Not the Same as Active Infection
This was an observational study of laboratory data without clinical details. Researchers did not know why patients were tested, whether they had symptoms, or whether positive results reflected a current illness or an exposure months or years earlier. False-positive and false-negative results were also possible, and the authors note that being positive for more than one pathogen does not prove active co-infection.
Readers should also weigh who produced the research. Quest Diagnostics sells tick-borne disease testing, including an antibody panel, and its researchers led the study.
Other research has found lower rates of active co-infection. A 2019 prospective study in the CDC journal Emerging Infectious Diseases of 52 untreated adults with the classic Lyme rash in New York found that nearly 90% had no evidence of co-infection, and Babesia was the only co-infection detected. Current treatment guidance has not changed based on the new study, and it remains unknown how many of the co-positive patients in the Quest data were actually sick with more than one infection.
The practical concern is treatment. Standard Lyme antibiotics, including first-line doxycycline, do not treat babesiosis, which requires a different combination of drugs. A missed Babesia infection can be dangerous for some patients.
"Our findings demonstrate a strikingly high rate of co-detection of antibodies against other tick-borne pathogens, particularly babesia," said lead author Yonghong Li, PhD, science director at Quest.
Symptoms and Next Steps After a Tick Bite
Lyme disease often causes fever, headache, fatigue, and sometimes an expanding red rash. Babesiosis and anaplasmosis can cause fever, chills, sweats, headache, and muscle aches, and symptoms of the three infections overlap. Babesiosis can also cause anemia, with dark urine or yellowing of the skin or eyes.
The people at greatest risk of severe babesiosis include older adults, people without a spleen, and people with weakened immune systems. Anyone in those groups who develops a fever after time outdoors in tick country should seek care promptly.
Adult blacklegged ticks remain active in cooler fall weather, so the risk does not end with summer. Tell your clinician about any tick bite or outdoor exposure, even without a rash. If Lyme treatment does not improve fever or other symptoms within a few days, ask whether testing for babesiosis or anaplasmosis is appropriate. Seek urgent care for high fever with confusion, shortness of breath, dark urine, or yellowing skin.
Prevention remains the best protection. Use an EPA-registered insect repellent, wear long sleeves and pants in wooded or grassy areas, and check your body, children, and pets for ticks after being outdoors. Remove attached ticks promptly with fine-tipped tweezers. Insurance often covers tick-borne disease testing when a clinician orders it for symptoms, although costs vary by plan.
The CDC estimates that up to about 476,000 people are diagnosed and treated for Lyme disease each year in the United States, according to CDC's Lyme disease information cited by Quest. Researchers say studies with clinical data will be needed to show how often these co-exposures reflect active disease. MedicalDaily will report on any updated clinical guidance.
Key Questions Answered
What did the study find? Among people with Lyme antibodies, 29.5% also had antibodies to at least one other tick-borne pathogen, compared with 5.5% of people without Lyme antibodies.
Does this mean those people had multiple infections? Not necessarily. Antibodies can reflect past exposure, and the study did not confirm active co-infection.
Which co-exposures were most common? Babesia and Anaplasma, both spread by blacklegged ticks. Babesia was co-detected in 18.5% of Lyme-positive patients in the Northeast.
Who faces the highest risk of severe illness? Older adults, people without a spleen, and people with weakened immune systems face a higher risk of severe babesiosis.
Why does co-infection matter for treatment? Doxycycline treats Lyme disease but not babesiosis, which requires different medications.
How can I lower my risk? Use EPA-registered repellent, cover skin outdoors, check for ticks daily, and remove attached ticks promptly.
Published by Medicaldaily.com
