Can Lyme Disease Relapse After Treatment? The Role of Babesia Coinfection
Symptoms may improve before returning
Babesia coinfection is one possible explanation
Recognition may guide a more complete evaluation
A patient experienced meaningful improvement after completing initial Lyme disease treatment. For several weeks, fatigue eased, thinking became clearer, and joint pain diminished. Activities that had been postponed began to feel possible again.
This pattern of Lyme disease relapse associated with Babesia coinfection is one of the most confusing challenges patients face after treatment.
This relapse pattern after Lyme disease treatment is more common than many patients realize and may point to an overlooked factor: Babesia coinfection.
Can Lyme Disease Relapse After Treatment?
Relapse after Lyme disease treatment can occur for several reasons. Treatment duration may have been insufficient, immune function may be be impaired, infection-related inflammation may persist despite appropriate therapy, or patients may experience reinfection after another tick bite. In some cases, symptoms attributed to relapse reflect a different underlying process.
One commonly overlooked explanation is untreated tick-borne coinfection. When antibiotics suppress Lyme disease but do not address other pathogens, partial improvement may occur. When treatment stops, symptoms return—not necessarily because Lyme disease persists, but because another infection remains active.
Babesia is one of the more important coinfections to consider when this pattern occurs. Identifying coinfections earlier may reduce the risk of recurrent symptoms and help guide appropriate treatment.
Some patients describe recurrent symptoms as a “Lyme flare-up.” Although the term is commonly used, the underlying explanation may differ from patient to patient and deserves careful evaluation.
Understanding Babesia Coinfection in Lyme Disease Relapse
Babesia is a microscopic parasite that infects red blood cells, similar to malaria. Unlike Lyme disease, which is caused by the bacterium Borrelia burgdorferi, Babesia is a protozoal infection and requires different medications for effective treatment. Standard Lyme antibiotics do not treat Babesia.
In regions where Lyme disease is endemic, Babesia exposure is not uncommon. A single tick bite can transmit both infections.
A large 2024 U.S. retrospective study of 3,521 patients diagnosed with babesiosis found that 42% had at least one documented tick-borne coinfection, with Lyme disease being the most common (41%). The study demonstrates how frequently these infections overlap, although it does not establish that Babesia is the cause of symptom relapse after Lyme disease treatment.
When Lyme disease is treated alone, Babesia may remain unrecognized and continue to cause symptoms that resemble relapse or treatment failure.
Although this article focuses on Babesia, other tick-borne coinfections—including Bartonella and Anaplasma—may also contribute to persistent or recurrent symptoms in selected patients.
Symptoms That May Suggest Babesia After Lyme Disease Treatment
Certain symptoms may raise suspicion for Babesia, particularly in patients who experience recurrent symptoms after Lyme disease treatment.
Night sweats and temperature dysregulation are among the more characteristic features and may be described as drenching sweats or unexplained hot-and-cold sensations.
Unexplained shortness of breath or air hunger may occur, even without known lung or heart disease. Fatigue is often more severe than what is typically seen with Lyme disease alone. Some patients also report pressure-type headaches that differ from prior headache patterns.
These symptoms are not specific to Babesia, but together with relapse after Lyme disease treatment they may warrant further evaluation.
Why Babesia Is Often Missed
Laboratory testing for Babesia has important limitations. A peripheral blood smear may fail to detect infection when the parasitic burden is too low, making diagnosis more difficult. Antibody results must also be interpreted in the context of symptom timing, exposure history, and other clinical findings.
Because of these limitations, experienced clinicians often consider the complete clinical picture rather than relying on a single negative laboratory test. When suspicion remains high, repeat blood smears, PCR testing, or additional evaluation may be appropriate.
How Response to Babesia Treatment May Inform Follow-up
When confirmed or strongly suspected Babesia is appropriately treated with antiprotozoal therapy, symptoms such as night sweats, air hunger, fatigue, and fever may improve. Clinical response can help guide follow-up, but it should not be used alone to establish the diagnosis because symptom improvement is not specific to Babesia.
A Broader View of Tick-Borne Illness
Tick-borne illness is rarely a single-pathogen condition. When Lyme disease treatment leads to improvement followed by recurrent symptoms, a broader evaluation is often warranted. This does not mean every relapse reflects Babesia, nor does it necessarily mean Lyme disease was inadequately treated.
Instead, clinicians may consider reinfection, persistent inflammation, untreated coinfections, or other medical conditions that can produce similar symptoms. A careful clinical evaluation helps determine the most likely explanation.
Coinfections such as Babesia are part of a broader pattern seen in complex tick-borne illness and should be considered alongside other possible causes of recurrent symptoms.
For Patients Experiencing Relapse
Relapse after Lyme disease treatment deserves careful evaluation. While many factors can contribute, coinfections such as Babesia may be part of the explanation. The goal is not simply to add another diagnosis but to identify factors that may be preventing a more complete recovery.
Patients whose symptoms recur despite initial improvement should discuss persistent or new symptoms with their healthcare professional. Additional evaluation may be appropriate depending on the clinical history, physical examination, and laboratory findings.
Frequently Asked Questions
Does every Lyme disease relapse mean Babesia is present?
No. Relapse after Lyme disease treatment can occur for many reasons, including reinfection, persistent inflammation, untreated coinfections, or unrelated medical conditions. Babesia is one possible contributor, particularly when characteristic symptoms or treatment patterns are present.
Can Lyme disease come back years later?
Symptoms returning years later do not necessarily mean the original Lyme disease infection has relapsed. Reinfection from another tick bite, untreated coinfections such as Babesia, persistent symptoms after Lyme disease, or another medical condition should all be considered during evaluation.
Can treated Lyme disease return?
Symptoms may return after treatment for several reasons. These include reinfection, untreated coinfections such as Babesia, persistent inflammation, or, in selected cases, persistent infection. A careful clinical evaluation helps determine the most likely explanation.
Is a Lyme flare-up the same as relapse?
Not necessarily. Many patients use the term “Lyme flare-up” to describe worsening symptoms. Depending on the situation, symptoms may reflect inflammation, reinfection, untreated coinfections, or another medical condition rather than a true relapse.
Can Babesia occur without Lyme disease?
Yes. Babesia can occur as a standalone infection, although coinfection with Lyme disease is common in regions where both infections are transmitted by Ixodes ticks.
Why don’t standard Lyme antibiotics treat Babesia?
Babesia is a protozoal parasite rather than a bacterium. As a result, it requires antiprotozoal medications such as atovaquone combined with azithromycin or other recommended regimens rather than standard Lyme disease antibiotics alone.
Clinical Takeaway
Improvement followed by recurrent symptoms after Lyme disease treatment does not always indicate treatment failure. Reinfection, persistent inflammation, untreated tick-borne coinfections—including Babesia—should all be considered during a careful clinical evaluation.
Recognizing Babesia coinfection as one possible explanation for recurrent symptoms may lead to a more complete evaluation and more appropriate treatment in selected patients.
Related Articles
Persistent Lyme Disease: An Overview
Night Sweats: An Overlooked Symptom of Babesia
References
- Krause PJ. Human babesiosis. International Journal for Parasitology. 2019;49(2):165–174.
- Kumar A, O’Bryan J, Krause PJ. The global emergence of human babesiosis. Pathogens. 2021;10(11):1447.
- Ssentongo P, Venugopal N, Zhang Y, Chinchilli VM, Ba DM. Beyond human babesiosis: Prevalence and association of Babesia coinfection with mortality in the United States, 2015–2022: A retrospective cohort study. Open Forum Infectious Diseases. 2024;11(10):ofae504.
- Zimmer AJ, Simonsen KA. Babesiosis. StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; updated August 6, 2025.
- Krause PJ, Auwaerter PG, Bannuru RR, Branda JA, Falck-Ytter YT, Lantos PM, et al. Clinical Practice Guidelines by the Infectious Diseases Society of America (IDSA): 2020 Guideline on Diagnosis and Management of Babesiosis. Clinical Infectious Diseases. 2021;72(2):e49–e64.
- Vannier E, Krause PJ. Human babesiosis. New England Journal of Medicine. 2012;366(25):2397–2407.
- Centers for Disease Control and Prevention. About babesiosis.
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
