Tick-Borne Diseases Beyond Lyme: What Doctors May Miss
Emerging tick-borne infections may mimic Lyme disease.
Testing is often limited or unavailable.
Delayed diagnosis can complicate treatment decisions.
Ticks carrying Borrelia burgdorferi may transmit far more than Lyme disease alone. In addition to common coinfections such as Babesia and Bartonella, clinicians increasingly face emerging and rare tick-borne infections that complicate diagnosis and treatment.
These infections include Borrelia miyamotoi, Rocky Mountain spotted fever (RMSF), Bourbon virus, Heartland virus, Borrelia mayonii, and Southern tick-associated rash illness (STARI).
Many of these illnesses are underrecognized because symptoms overlap with Lyme disease, testing is limited, and clinician awareness remains variable.
For a broader overview of overlapping infections, visit our Lyme Coinfections Guide.
Borrelia miyamotoi
Borrelia miyamotoi is a relapsing fever spirochete transmitted by the same Ixodes scapularis ticks that carry Lyme disease.
Unlike Lyme disease, patients often present without the classic erythema migrans rash. Symptoms may include:
- Fever
- Headache
- Fatigue
- Muscle aches
- Relapsing flu-like illness
Standard Lyme disease testing does not reliably detect Borrelia miyamotoi, which can lead to negative Lyme testing despite ongoing symptoms after tick exposure.
Diagnosis typically requires PCR or specialized serologic testing.
Doxycycline remains first-line treatment.
Rocky Mountain Spotted Fever (RMSF)
Rocky Mountain spotted fever is a potentially severe bacterial infection caused by Rickettsia rickettsii.
Despite its name, RMSF occurs throughout the United States and is especially common in southeastern regions.
Symptoms may include:
- High fever
- Severe headache
- Muscle aches
- Rash
- Confusion
- Gastrointestinal symptoms
The rash may appear late or may never develop, contributing to delayed diagnosis.
Because RMSF can become life-threatening, doxycycline treatment should begin based on clinical suspicion without waiting for confirmatory testing.
Learn more in Atypical Presentation of RMSF.
Bourbon Virus
Bourbon virus is a rare emerging tick-borne virus first identified in Kansas in 2014.
Reported symptoms include:
- Fever
- Fatigue
- Rash
- Nausea
- Body aches
- Headache
Testing is limited to specialized laboratories, and there is currently no specific antiviral treatment.
Severe illness and fatal cases have been reported.
Heartland Virus
Heartland virus is another emerging tick-borne viral illness associated primarily with lone star ticks.
Symptoms may include:
- Fever
- Fatigue
- Loss of appetite
- Muscle aches
- Nausea
- Low white blood cell counts
Like Bourbon virus, treatment is supportive because no specific antiviral therapy currently exists.
The true number of infections may be underestimated because testing remains limited.
Borrelia mayonii
Borrelia mayonii is a recently identified Lyme disease-causing spirochete found primarily in the upper Midwest.
Symptoms may resemble Lyme disease but sometimes include:
- Diffuse rash
- Nausea
- Vomiting
- Higher bacterial levels in the bloodstream
Standard Lyme disease testing may not reliably detect all cases.
Treatment generally follows standard Lyme disease protocols using doxycycline or amoxicillin.
STARI (Southern Tick-Associated Rash Illness)
STARI presents with a rash that closely resembles the erythema migrans rash seen in Lyme disease.
However, STARI occurs primarily in regions where Lyme disease is less common and is associated with lone star tick exposure.
The exact cause of STARI remains uncertain.
Symptoms may include:
- Expanding rash
- Fatigue
- Headache
- Muscle aches
Unlike Lyme disease, STARI does not appear to cause chronic neurologic, cardiac, or arthritic complications.
Why These Infections Are Often Missed
Rare and emerging tick-borne infections are frequently overlooked because:
- Symptoms overlap with Lyme disease
- Testing may be unavailable or limited
- Clinician awareness varies
- Geographic assumptions may bias diagnosis
- Patients may test negative for Lyme disease despite tick exposure
Patients with fever, rash, fatigue, neurologic symptoms, or flu-like illness after tick exposure may require broader evaluation beyond standard Lyme testing alone.
Learn more about Lyme Disease Misdiagnosis.
Why Geographic Expansion Matters
Tick populations and tick-borne pathogens continue to expand geographically.
Clinicians increasingly encounter infections previously considered rare or regionally limited.
This expanding overlap between pathogens may complicate diagnosis because multiple infections can circulate within the same geographic region.
Learn more about Prevention of Lyme Disease.
Frequently Asked Questions
What are rare tick-borne infections?
Rare tick-borne infections include illnesses such as Borrelia miyamotoi, Bourbon virus, Heartland virus, RMSF, and STARI.
Can you have multiple tick-borne infections at once?
Yes. A single tick bite may transmit more than one pathogen simultaneously.
Do standard Lyme tests detect these infections?
No. Many emerging tick-borne infections require specialized testing not included in standard Lyme disease panels.
Do all tick-borne infections respond to doxycycline?
No. Some bacterial infections respond to doxycycline, but viral infections such as Bourbon virus and Heartland virus do not have specific treatments.
Why are these infections often missed?
Symptoms overlap with Lyme disease, testing is limited, and some clinicians may be unfamiliar with emerging pathogens.
Clinical Takeaway
Emerging tick-borne infections beyond Lyme disease may present with overlapping symptoms, negative Lyme testing, and delayed diagnosis.
As tick populations expand and new pathogens emerge, broader clinical awareness may become increasingly
Related Articles
Learn more about relapsing fever infections in What Is Borrelia miyamotoi?.
Learn more about delayed recognition in Delayed Lyme Disease Diagnosis.
Learn more about STARI in Southern Tick-Associated Rash Illness (STARI) and Lyme Disease.
Review broad symptom patterns in Lyme Disease Symptoms Guide.
Review neurologic complications in Neurologic Lyme Disease.
References
- Krause PJ, et al. Borrelia miyamotoi sensu lato seroreactivity and seroprevalence in the northeastern United States. Emerg Infect Dis. 2014;20(7):1183-1190.
- Biggs HM, et al. Diagnosis and Management of Tickborne Rickettsial Diseases: Rocky Mountain Spotted Fever and Other Spotted Fever Group Rickettsioses, Ehrlichioses, and Anaplasmosis. MMWR Recomm Rep. 2016;65(2):1-44.
- Pritt BS, et al. Identification of a novel pathogenic Borrelia species causing Lyme borreliosis with unusually high spirochaetaemia: a descriptive study. Lancet Infect Dis. 2016;16(5):556-564.
Dr. Daniel Cameron, MD, MPH
Lyme disease clinician with over 30 years of experience and past president of ILADS.
Symptoms • Testing • Coinfections • Recovery • Pediatric • Prevention
