Lyme Disease Co-Infections: Symptoms, Testing, and Treatment
STILL SICK AFTER LYME TREATMENT?
CO-INFECTIONS MAY BE THE MISSING PIECE
“Why am I not getting better?”
For many patients, the answer isn’t Lyme disease alone—it’s co-infections.
Quick Answer: Lyme disease co-infections occur when a tick transmits more than one pathogen, often leading to more severe or persistent illness.
Clinical Insight: When symptoms are atypical, severe, or resistant to treatment, clinicians should consider additional tick-borne infections.
Black-legged ticks can carry bacteria, parasites, and viruses capable of infecting humans at the same time.
The CDC reports that “a single tick can transmit multiple pathogens.” [1]
These co-infections may make patients sicker, prolong illness, and require different treatment than Lyme disease alone.
Common symptoms of Lyme co-infections
Co-infections often change the clinical picture.
Symptoms may be more severe, prolonged, or different from typical Lyme disease.
- High fevers or chills
- Drenching sweats
- Severe fatigue
- Headaches
- Shortness of breath
- Neurologic symptoms
- Psychiatric symptoms
- Swollen glands
- Muscle and joint pain
When symptoms don’t follow the expected pattern, additional infections should be considered.
Ticks can carry multiple pathogens
Studies show that many ticks carry more than one disease-causing organism.
In one study, up to 67% of ticks carried at least one pathogen, and many carried more than one.
In endemic regions, co-infection rates may reach 28% or higher.
Some ticks carry multiple microbes at the same time.
How common are co-infections in patients?
Clinical studies show co-infections are common in Lyme patients.
- Up to 40% of Lyme patients may have Babesia
- 1 in 3 Babesia patients may also have Anaplasmosis
- Many Babesia cases occur alongside Lyme disease
This overlap helps explain why some patients do not respond to Lyme treatment alone.
Why co-infections are often missed
Co-infections are frequently overlooked due to:
- Overlapping symptoms with Lyme disease
- Limited or insensitive testing
- Lack of routine screening for additional infections
- Need for specialized laboratory testing
In one analysis, only 17% of tick-borne disease samples were tested for infections beyond Lyme disease.
As a result, many co-infections go undiagnosed.
Most common Lyme co-infections
- Babesia
- Anaplasmosis
- Ehrlichia
- Bartonella
- STARI
- Borrelia miyamotoi
Babesia
Babesia is a parasite that infects red blood cells.
Symptoms often include fever, chills, sweats, fatigue, and shortness of breath.
Co-infection with Babesia may worsen symptoms and prolong illness.
Anaplasmosis
Anaplasmosis is caused by Anaplasma phagocytophilum.
Symptoms include fever, headache, fatigue, and muscle aches.
Some cases require hospitalization.
Bartonella
Bartonella species are associated with neurologic and psychiatric symptoms in some patients.
Symptoms may include fatigue, lymph node swelling, and neurologic changes.
STARI
STARI is an emerging illness that resembles Lyme disease.
It occurs primarily in the southeastern United States.
Long-term outcomes remain uncertain.
Borrelia miyamotoi
Borrelia miyamotoi causes a relapsing fever-like illness.
Symptoms include fever, headache, fatigue, and muscle aches, often without a rash.
Clinical takeaway
Co-infections are a common and often overlooked part of Lyme disease.
When symptoms are severe, persistent, or don’t respond to treatment, co-infections should be considered.
Recognizing them can change both diagnosis and treatment.
Frequently Asked Questions
Can you have Lyme disease and Babesia at the same time?
Yes. Babesia is one of the most common co-infections and may worsen symptoms or prolong illness.
Do co-infections require different treatment?
Yes. Some infections, such as Babesia, require different medications than Lyme disease.
Why are co-infections missed?
Symptoms overlap, testing is limited, and patients are not always evaluated for additional infections.
When should co-infections be suspected?
When symptoms are severe, persistent, or do not respond to standard Lyme treatment.
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
Thank you! My daughter just tested positive for Babesia Duncani and Bartonella Bacilliformis. I am thankful to find your blog! There is one Lyme specialist in our state and I understand he sometimes has a 6-month waiting list. So the info you share is very helpful to us!
What are the tests for lymes disease co- infections? How does one find a doctor that specializes in lymes disease? I’m in Arizona, and was diagnosed 20 years ago.