Babesia and the Blood Supply: What Patients Need to Know

Babesia blood supply risk is an underrecognized public health issue—this parasite can spread through transfusions, even when donors have no symptoms.

Babesia blood supply safety is one of the most overlooked public health issues in tick-borne disease. While most people associate Babesia with tick bites, this malaria-like parasite can also spread through blood transfusions, blood donations, and from mother to child during pregnancy.

More than 200 cases of transfusion-transmitted babesiosis have been reported in the United States, making Babesia the leading parasitic infection transmitted through the blood supply.

This page explains how Babesia enters the blood supply, where screening falls short, and what patients and clinicians need to know to reduce risk.

How Babesia Enters the Blood Supply

Unlike Lyme disease, which has not been confirmed to spread through blood transfusion, Babesia can survive in stored blood products—including red blood cells, platelets, and plasma.

When an infected person donates blood, the parasite can be transmitted to the recipient.

Many donors have no symptoms. Asymptomatic carriers can unknowingly donate infected blood.

An FDA public workshop confirmed that Babesia is now the most significant transfusion-transmitted parasitic infection in the United States—surpassing malaria, which has been largely controlled through donor screening.

Transfusion-Transmitted Babesiosis

Transfusion-transmitted babesiosis occurs when a patient receives blood contaminated with Babesia microti.

The consequences can be severe—especially for:

• Immunocompromised patients
• Elderly individuals
• Patients requiring chronic transfusions

In one case, a single unit of blood changed everything for a patient with sickle cell disease.

Cases have also been reported in non-endemic states, challenging the assumption that Babesia is limited to certain regions.

Babesia Blood Supply Risk to Newborns

Premature infants are among the most vulnerable populations.

In one report, three premature infants in one NICU contracted Babesia from a single donor who passed standard screening.

Two infants developed high parasitemia. One relapsed after treatment—highlighting the difficulty of managing infection in this population.

This case underscores a critical gap: current screening methods may not detect all infections.

Congenital Transmission: Mother to Child

Babesia can also be transmitted during pregnancy.

Cases of mother-to-child transmission demonstrate how infection can affect newborns even without transfusion.

Additional reports include:

• A 5-week-old twin
• Additional neonatal cases

Clinicians should consider Babesia in newborns with unexplained illness—especially if there has been transfusion or maternal tick exposure.

Why Donor Screening Falls Short

Current screening relies heavily on questionnaires about tick exposure and travel history.

However, research presented at the FDA workshop on Babesia found no correlation between donor responses and actual infection.

Key challenges include:

• Many infected donors are asymptomatic
• Screening is not universal across all states
• A single donor can infect multiple recipients
• Parasites survive throughout blood storage

By comparison, malaria has been reduced to fewer than one transfusion case per year through improved screening—something Babesia has not yet achieved.

Babesia vs Lyme Disease in the Blood Supply

Patients often ask whether Lyme disease can be transmitted through blood transfusion.

Although Borrelia burgdorferi can survive briefly in blood products, there have been no confirmed cases of Lyme disease transmitted this way.

Babesia microti, by contrast, reaches higher concentrations in red blood cells—allowing it to survive storage and infect recipients.

This is why Babesia—not Lyme disease—is the dominant transfusion-transmitted tick-borne infection.

What Needs to Change

The growing number of cases highlights the need for improved safeguards.

• Universal Babesia screening—not limited to endemic states
• Molecular (PCR-based) testing in addition to antibody screening
• Greater clinician awareness of transfusion-related infection
• Higher suspicion for Babesia in post-transfusion fevers

Until screening improves, both patients and clinicians should recognize that Babesia can be transmitted through the blood supply—not just through tick exposure.

Frequently Asked Questions

Can you get Babesia from a blood transfusion?
Yes. More than 200 cases have been reported in the United States.

Is Lyme disease transmitted through transfusion?
No confirmed cases have been documented.

Does donor screening prevent Babesia transmission?
Not reliably. Questionnaire-based screening often fails to detect infection.

Can a mother pass Babesia to her baby?
Yes. Congenital transmission has been documented.

Who is most at risk?
Immunocompromised patients, elderly individuals, premature infants, and those requiring frequent transfusions.

Related Reading

• Babesia and Lyme: What Patients Need to Know
• Babesia Blood Donation: When Screening Finds Infection
• Babesia Pregnancy and Transmission
• Congenital Babesia Case
• Lyme Disease Co-infections

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