Anthony Stitt
2026-01-15 21:02:00
January 15, 2026
3 min read
Key takeaways:
- A bite from the lone star tick produces a “bull’s-eye” rash indistinguishable from Lyme disease.
- The tick is migrating into Mid-Atlantic states and southern New England and could move farther north.
Lone star ticks, which originated in the southern United States, are on the move, potentially complicating the diagnosis of tickborne diseases in areas where they now overlap with ticks that cause Lyme disease, according to experts.
The ticks are heading north and causing southern tick-associated rash illness (STARI), which produces a “bull’s-eye” rash indistinguishable from the rash caused by Lyme disease, the experts cautioned in a correspondence published this week in The New England Journal of Medicine.
Lone star ticks are moving north, potentially complicating the diagnosis of tickborne diseases in areas where they now overlap with ticks that cause Lyme disease, experts say. Image: Adobe Stock.
The similar-looking rashes can make diagnosing Lyme disease trickier; however, STARI is less severe than Lyme disease, often self-resolving, and lacks long-term neurological and arthritic symptoms.
For an explanation on the impact of the migrating ticks, Healio spoke to Raymond J. Dattwyler, MD, professor of microbiology/immunology and medicine at New York Medical College, who coauthored the correspondence.
Healio: How and why has the distribution of the lone star tick (Amblyomma americanum) changed, and where are they overlapping now with ticks that cause Lyme disease?
Dattwyler: We don’t know what’s causing the overlapping. They’re overlapping throughout the Mid-Atlantic and into southern New England. The trouble is they’re shifting and could spread in northern parts of New England.
Healio: How is the changing epidemiology complicating the diagnosis of Lyme disease and STARI?
Dattwyler: The certainty that the rash (Erythema migrans) is diagnostic of Lyme disease is significantly diminished. So, what we need are better diagnostic tests, which are being developed.
Healio: What are the clinical implications of these changes, and how should clinicians in these areas alter current practices?
Dattwyler: It makes the diagnosis of Lyme disease tougher. I’ve seen thousands of Lyme disease cases, and I can’t tell the difference between Erythema migrans and STARI. You can no longer say you definitely have Lyme disease. For the average physician, treat them as if they had Lyme disease. You still follow them up and still do appropriate testing. If I were a PCP and saw the lesion, I would treat it with doxycycline, even though you can no longer definitely say it’s Lyme. It’s safer to treat than not to treat. The risk of missing Lyme is greater than the risk of giving someone doxycycline or amoxicillin who doesn’t need it.
Healio: Do we know to what extent STARI occurs in the Mid-Atlantic states?
Dattwyler: It’s fairly common in the Mid-Atlantic states but we don’t have exact numbers.
Healio: Does STARI resolve on its own without antibiotic treatment? And, if it does, what percentage of cases are resolved without treatment?
Dattwyler: Yes, it resolves on its own. We’re not even sure what’s even causing it. People have looked for bacteria and viruses and have not come to a definite conclusion.
Healio: Is it expected that STARI will surpass Lyme disease in cases in the Mid-Atlantic?
Dattwyler: Unknown.
Healio: Are there emerging tools or technologies that may simplify the distinction between Lyme disease and STARI?
Dattwyler: We have the PCR that can diagnosis Lyme disease but the biggest problem with it is you must do a skin biopsy, and the average physician and the patient don’t want to do a skin biopsy. We’re essentially working on a workaround. When will we develop diagnostic tools? One will never know.
Healio: Because medical guidance of STARI is based on similarity to Lyme disease, do you expect guidance to become more specific to STARI?
Dattwyler: Right now, no. I can’t predict the future.
Healio: Other than the indistinguishable rash, are there any other problems caused by the migrating tick?
Dattwyler: The biggest problem is the meat-allergy question. For whatever reason, lone star tick bites can cause an allergy to alpha-gal, which is in beef and pork. You could get delayed anaphylaxis that can happen up to 6 or more hours after eating meat. There’s one anaphylaxis death that I’m aware of. [Editor’snote:Thedeathwhichwas[Editor’snote:Thedeathwhichwasdescribed recently in a journal, occurred in 2024.]
Healio: Do you expect STARI to impact other regions beyond the Mid-Atlantic, perhaps into areas farther north?
Dattwyler: That’s a definite maybe. I would expect that it would. When and to what degree, I don’t know. I know it’s not around Boston yet.
For more information:
Raymond J. Dattwyler, MD, can be reached at [email protected].
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