Babesia Undertesting in Lyme Disease: Why Co-Infections Are Still Missed
The Lyme test is positive.
Treatment begins—but symptoms persist.
This is where Babesia can be missed.
Babesia undertesting in Lyme disease remains a significant gap in diagnosis—and may explain why some patients do not fully recover.
This is one of the most common reasons symptoms persist after Lyme disease treatment.
This is where one infection can overshadow another.
A large study examining nearly 3 million specimens found that only 3% included testing for Babesia, despite known co-infection rates.
This reflects a broader gap in Lyme disease co-infection diagnosis.
Start here: Lyme disease symptoms guide
How Often Is Babesia Tested in Lyme Disease?
Are patients routinely tested for Babesia?
The scale of undertesting becomes clear in large laboratory data.
- 2,978,881 total tick-borne disease specimens
- Only 85,323 included Babesia testing
- 2,432,396 were tested for Lyme disease
This means Lyme testing was ordered nearly 30 times more often than Babesia testing.
This is where undertesting becomes clinically important.
How Common Is Babesia Co-Infection?
How often do Lyme patients also have Babesia?
Babesia is one of the most common Lyme disease co-infections in endemic regions.
A study published in Vector-Borne and Zoonotic Diseases found that 28.6% of Lyme patients tested positive for Babesia microti.
Other studies report co-infection rates ranging from 10% to 32%, with some estimates approaching 40%.
These patterns suggest Babesia co-infection may be more common than testing practices reflect.
Why Babesia Undertesting Matters
What happens when Babesia is missed?
Babesia requires a different treatment approach than Lyme disease.
Doxycycline does not treat Babesia.
Instead, treatment typically includes antiparasitic therapy such as atovaquone combined with azithromycin.
This is where symptoms may persist despite appropriate Lyme treatment.
Patients may continue to experience:
- Fatigue
- Night sweats
- Air hunger
- Cyclical symptoms
In these cases, symptoms may reflect untreated co-infection rather than treatment failure alone.
Why Babesia May Be Missed in Children
Are children at higher risk of being overlooked?
Studies suggest higher rates of Babesia infection in children ages 1 to 10.
This is where diagnosis becomes more difficult.
Symptoms may overlap with common childhood illnesses, and children may not clearly describe symptoms such as air hunger or night sweats.
Without targeted testing, Babesia may be overlooked.
Why Babesia Matters Beyond Lyme Disease
This is where public health implications emerge.
Babesia microti is the most commonly reported transfusion-transmitted pathogen in the United States without universal donor screening.
This highlights the broader importance of recognizing Babesia infection.
When Should Babesia Testing Be Considered?
Who should be tested?
Babesia testing may be considered in patients with:
- Confirmed or suspected Lyme disease
- Persistent symptoms after treatment
- Unexplained anemia or low platelets
- Night sweats, air hunger, or cyclical fevers
This is where clinical suspicion becomes critical.
Learn more: Babesia testing
Clinical Takeaway
Babesia undertesting represents a gap between co-infection rates and current testing practices.
Recognizing co-infections may explain persistent symptoms and guide more effective treatment.
If symptoms persist after Lyme treatment, it’s worth asking whether Babesia has been missed.
Related Reading
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
