Can Babesiosis Cause a False-Positive HIV Test?
Positive HIV test—but no HIV?
Babesiosis may be the reason.
Here’s what one case revealed.
A babesiosis false positive HIV test is rare—but documented. Investigators described a patient with acute babesiosis who initially tested positive for HIV, only to have repeat testing turn negative after treatment.
This case highlights an important clinical point: not every positive test result reflects true infection.
Case: Babesiosis With a Positive HIV Test
A 60-year-old man presented with intermittent fever, fatigue, anorexia, and worsening jaundice over three weeks. Laboratory testing revealed parasites in the blood, and a smear confirmed Babesia microti with 1–2% of red blood cells infected.
Despite the relatively low level of parasitemia, the patient appeared severely ill. Because of this discrepancy, clinicians expanded the evaluation and performed HIV testing.
The fourth-generation HIV 1/2 antigen/antibody test returned positive.
Why the HIV Test Was Misleading
After treatment for babesiosis, repeat HIV testing was negative.
This confirmed the initial result was a false-positive HIV test.
The authors noted that while fourth-generation HIV tests are highly accurate, false positives can occur—particularly in the setting of acute infections like babesiosis.
How Babesiosis May Interfere With Testing
The exact mechanism is not fully understood, but acute infections can trigger immune responses that interfere with antibody-based testing.
In babesiosis, immune activation and circulating antigens may contribute to cross-reactivity in laboratory assays.
Although rare, this phenomenon has been described in several case reports.
Treatment and Outcome
The patient was treated with:
- Atovaquone and azithromycin for babesiosis
- Doxycycline to cover possible co-infections
Due to the severity of illness, an exchange transfusion was also performed.
Following treatment:
- Symptoms resolved
- Repeat HIV testing was negative
This confirmed the HIV result was not a true infection.
Why This Case Matters Clinically
False-positive HIV tests are uncommon, but they can have serious emotional and clinical consequences.
This case reinforces an important principle:
- Unexpected test results should be confirmed
- Clinical context matters
- Tick-borne infections can complicate interpretation
For clinicians managing tick-borne diseases, especially Babesia, awareness of this possibility can prevent misdiagnosis.
Common Sense Lyme Takeaway
If a patient with acute babesiosis tests positive for HIV, do not assume the result is definitive.
- Repeat testing is essential
- Consider false positives in acute infection
- Evaluate the full clinical picture
Sometimes the test is wrong—not the patient.
Related Articles
- Can Lyme disease trigger a cascade of costly, unnecessary tests?
- Neurologic complications of Babesia
- Can a tick be tested for Lyme disease?
References:
- He JZ et al. Acute Babesiosis Causing a False-Positive HIV Result: An Unexpected Association. Case Rep Infect Dis. 2023.
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
I hope this information is quickly spread to all the medical schools. They are so dragging their feet on anything tick-borne related. We are losing generations. You and Lyme disease.org are doing their work for them. Thank you…