When we think of tick-borne illnesses like Babesia, we often picture outdoor exposure in wooded, high-risk areas. But what happens when Babesia shows up in someone who hasn’t been outdoors—and hasn’t been bitten by a tick? One recent case reminds us that Babesia can travel silently through the bloodstream, sometimes delivered unintentionally through a blood transfusion.

A 30-year-old man with sickle cell disease (SCD) required regular red blood cell exchanges—about 10 units every 3 to 4 weeks since childhood. Two months after a routine blood transfusion, he developed symptoms that initially seemed vague: fever, neck pain, and photophobia.

But within days, his condition worsened. He experienced:

1. Persistent fever and chills
2. Headache
3. Fatigue
4. Loss of appetite

It was clear something serious was unfolding.

A Surprising Diagnosis – Babesia via a blood transfusion

Lab work confirmed the presence of Babesia parasites in his red blood cells, and serologic testing came back positive. He was also borderline positive for Anaplasma phagocytophilum and Ehrlichia chaffeensis, though not treated for those due to a lack of supportive symptoms.

Babesia is a malaria-like parasite typically spread by ticks, but this patient hadn’t been outdoors or hiking recently. So, where had it come from?

Tracing the Source: A Lookback Investigation

A donor lookback investigation revealed the answer. Over six months, the patient had received blood transfusions including 65 units of blood—58 of which were screened for Babesia. One of the 7 unscreened units came from a donor who tested positive for Babesia microti.

This donor lived in Ohio, a state not considered endemic for Babesia and thus not required to screen blood donors for the parasite. The donor reported no symptoms and had been active outdoors, hiking and camping in Ohio, Tennessee, and North Carolina—states with potential but under-recognized risk for tick exposure.

Why This Matters: A Vulnerable Blood Supply

This case, published by Costa and colleagues,¹ highlights a critical issue: transfusion-transmitted babesiosis (TTB) remains a real and preventable risk—especially in patients with chronic blood transfusion needs, like those with sickle cell disease.

“Prior to laboratory-based blood donor screening for Babesia, TTB was a leading infectious risk to the blood supply in the United States,” the authors note.

In 2019, the FDA implemented Babesia screening requirements for blood donors in 14 high-incidence states, including Connecticut, Massachusetts, New York, and Minnesota. But states like Ohio—where this case originated—are not yet on that list.

A Simple Treatment, a Critical Delay

Fortunately, this patient was promptly treated with a 10-day course of azithromycin and atovaquone, and his symptoms resolved. But in many cases, particularly in non-endemic states, the delay in diagnosis can lead to more severe disease, especially in vulnerable populations.

Lessons for Clinicians and Policymakers

This case reminds us of a few important lessons:

🩸 1. Babesia Isn’t Just Tick-Borne

Yes, it’s a tick-borne disease—but it’s also transmissible via blood transfusions. That means even patients without outdoor exposure can be at risk.

🌎 2. “Non-Endemic” Doesn’t Mean No Risk

Donors may travel, camp, or hike in high-risk areas—even if their home state isn’t considered endemic. Geographic assumptions can lead to blind spots in our screening systems.

⏳ 3. Delays in Diagnosis Can Be Deadly

In places where clinicians aren’t used to seeing Babesia, diagnosis can be delayed. For immunocompromised or chronically transfused patients, that delay can be critical.

📋 4. Screening Policies May Need Expansion

We must reconsider whether the current state-specific Babesia screening recommendations are sufficient. This case suggests a broader approach may be warranted.

Final Thoughts

For patients like this young man with sickle cell disease, a single unscreened unit of blood changed everything. His case is a powerful reminder that Babesia is no longer just a disease of the woods—it’s also a disease of the blood bank.

As we continue to evolve our understanding of blood transfusion safety, infectious disease spread, and vector-borne illnesses, we must remain open to adjusting our protocols and awareness—even in states not currently labeled “high risk.”

Because in medicine, what we don’t test for can still hurt our patients.