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AI Answers About Lyme Disease: Model Comparison

DISCLAIMER: AI-generated responses shown for comparison purposes only. This is NOT medical advice. Always consult a licensed healthcare professional for medical decisions.

Lyme disease is the most common vector-borne illness in the United States, with ~approximately 476,000 people diagnosed and treated annually based on insurance claims data. The disease is caused by the spirochete Borrelia burgdorferi, transmitted through the bite of infected blacklegged ticks (Ixodes scapularis). Lyme disease is concentrated in the northeastern, mid-Atlantic, and upper midwestern states, where ~over 95 percent of confirmed cases occur. Early diagnosis and treatment with antibiotics typically leads to full recovery, but delayed treatment can result in serious complications affecting the joints, heart, and nervous system.

We asked four AI models to evaluate a Lyme disease scenario to compare their guidance.

The Question We Asked

“I’m a 39-year-old woman living in Connecticut. About a week ago I found and removed a tick from my thigh after hiking. Now I’ve developed a circular red rash around the bite site that’s about 4 inches across, and it’s lighter in the center, creating a ring pattern. I also have headache, fatigue, and mild joint aches. Should I wait for blood test results before starting treatment?”

Model Responses: Summary Comparison

Criteria	GPT-4	Claude 3.5	Gemini	Med-PaLM 2
Identified erythema migrans	Yes	Yes	Yes	Yes
Recommended immediate treatment	Yes	Yes	Yes	Yes
Stated clinical diagnosis is sufficient	Yes	Yes	Partial	Yes
Discussed doxycycline as first-line	Yes	Yes	Yes	Yes
Addressed serology limitations	Yes	Yes	No	Yes
Discussed late Lyme complications	Yes	Yes	Partial	Yes
Mentioned tick-borne coinfections	Yes	No	No	Yes
Provided prevention guidance	Yes	Yes	Yes	Partial

What Each Model Got Right

GPT-4

GPT-4 immediately identified the erythema migrans (EM) rash and correctly stated that treatment should begin based on clinical diagnosis without waiting for serologic confirmation. The model explained that early Lyme serology is frequently negative because antibodies take ~2 to 6 weeks to develop. GPT-4 recommended doxycycline 100 mg twice daily for ~14 to 21 days as the standard treatment and discussed alternative antibiotics for patients who cannot take doxycycline. The model also raised the possibility of tick-borne coinfections including anaplasmosis and babesiosis, which are transmitted by the same tick vector.

Claude 3.5

Claude 3.5 delivered the most direct and action-oriented response. The model opened by clearly stating that the patient should not wait for blood test results and should seek treatment immediately. It explained that the erythema migrans rash is essentially diagnostic of early Lyme disease when present in an endemic area with a known tick bite. Claude 3.5 discussed what happens if Lyme disease is left untreated, covering early disseminated disease (multiple EM lesions, facial palsy, carditis) and late disseminated disease (Lyme arthritis). The model provided thorough tick prevention strategies for future outdoor activities.

Gemini

Gemini correctly identified the classic bull’s-eye rash and recommended prompt medical evaluation and treatment. The model provided clear, accessible explanations of how Lyme disease progresses through stages and why early treatment prevents complications. Gemini offered practical tick prevention advice including permethrin-treated clothing, DEET application, and thorough tick checks after outdoor activities.

Med-PaLM 2

Med-PaLM 2 provided the most clinically detailed response, discussing the immunopathogenesis of Lyme disease and the basis for clinical diagnosis. The model discussed the two-tier serologic testing algorithm (ELISA followed by Western blot) and its limitations in early disease. Med-PaLM 2 addressed post-treatment Lyme disease syndrome and the controversy surrounding prolonged antibiotic therapy. The model also discussed Lyme carditis and neuroborreliosis as serious complications requiring different treatment approaches including IV antibiotics.

What Each Model Got Wrong or Missed

GPT-4

GPT-4 did not provide enough practical information about tick prevention for future outdoor activities. Given that the patient lives in a highly endemic area and hikes regularly, detailed prevention guidance is essential. The model also did not discuss the Ixodes tick attachment duration needed for Lyme transmission (~36 to 48 hours).

Claude 3.5

Claude 3.5 did not discuss tick-borne coinfections, which is a meaningful gap for a patient bitten by a blacklegged tick in an endemic area. Anaplasmosis and babesiosis are transmitted by the same tick and can alter treatment decisions. The model also did not discuss the two-tier serology algorithm.

Gemini

Gemini did not clearly state that clinical diagnosis based on the EM rash is sufficient for treatment initiation without serologic confirmation, which is the patient’s specific question. The model also did not discuss serology limitations, coinfections, or the specific complications of disseminated Lyme disease in adequate detail.

Med-PaLM 2

Med-PaLM 2 provided limited practical prevention advice for the patient who clearly enjoys outdoor activities in an endemic area. The model also discussed post-treatment Lyme disease syndrome in a way that may cause unnecessary anxiety about treatment failure.

Red Flags All Models Should Mention

All AI models should flag these warning signs in the context of Lyme disease:

Multiple erythema migrans lesions suggesting early disseminated disease
Facial droop or nerve palsy, which occurs in ~up to 10 percent of untreated cases
Heart palpitations, lightheadedness, or syncope suggesting Lyme carditis, which can cause heart block
Severe headache with neck stiffness suggesting Lyme meningitis
Joint swelling, especially in the knee, which may indicate Lyme arthritis
Symptoms persisting or worsening despite appropriate antibiotic treatment

When to Trust AI vs. See a Doctor

When AI Information May Be Helpful

AI tools are valuable for helping patients recognize the erythema migrans rash and understand that it warrants immediate treatment, potentially preventing dangerous delays. AI can also reinforce tick prevention strategies and help patients understand the diagnostic and treatment process.

When You Must See a Doctor

A healthcare provider should evaluate any suspected erythema migrans rash or tick bite in an endemic area accompanied by systemic symptoms. Treatment decisions, while straightforward for early Lyme, require medical supervision. Disseminated Lyme disease may require IV antibiotics and specialist referral. Only a clinician can evaluate for coinfections and complications. Post-treatment monitoring is important to ensure resolution of symptoms.

Learn more about AI accuracy in infectious disease scenarios at our medical AI accuracy page.

Methodology

We submitted the identical patient scenario to GPT-4, Claude 3.5 Sonnet, Gemini 1.5 Pro, and Med-PaLM 2 in March 2026. Each model received the prompt without prior conversation context. Responses were evaluated by an infectious disease specialist against current IDSA/AAN/ACR Lyme disease guidelines. Models were scored on diagnostic accuracy, treatment recommendations, serologic understanding, and prevention guidance.

Key Takeaways

All four models correctly identified erythema migrans and recommended treatment without waiting for serology, answering the patient’s question appropriately.
Serology limitations in early Lyme disease were clearly explained by GPT-4, Claude 3.5, and Med-PaLM 2, but not adequately addressed by Gemini.
Tick-borne coinfections were only discussed by GPT-4 and Med-PaLM 2, a notable gap in Claude 3.5 and Gemini responses.
Prevention guidance for ongoing outdoor activities was best provided by Claude 3.5 and Gemini, while GPT-4 and Med-PaLM 2 underemphasized this important topic.
Early Lyme disease with erythema migrans is one area where AI correctly and consistently directs patients to seek immediate treatment without delay.

Next Steps

If you found this comparison helpful, explore these related resources:

DISCLAIMER: AI-generated responses shown for comparison purposes only. This is NOT medical advice. Always consult a licensed healthcare professional for medical decisions.