A Cluster of Transfusion-Associated Babesiosis Cases Traced to a Single Asymptomatic Donor

CONTEXT The risk of acquiring babesiosis by blood transfusion is largely unknown since in areas where it is endemic it is often an asymptomatic infection. OBJECTIVE To investigate and treat a cluster of blood transfusion–associated babesiosis cases. DESIGN Case series and epidemiologic investigation. SETTING Urban inner-city hospital. PATIENTS Six persons who received Babesia microti–infected blood components from a donor. MAIN OUTCOME MEASURE Diagnosis and successful therapy of babesiosis following transfusion. RESULTS Six individuals (1 adult, 1 child, and 4 neonates) were exposed to products from a single blood donation by an asymptomatic Babesia-infected donor. Three of the 6 exposed patients became parasitemic. Polymerase chain reaction testing, animal inoculation studies, and indirect immunofluorescent antibody testing were used to confirm the presence of Babesia microti in the donor's blood and to establish the presence of infection in 3 of the 6 recipients. The 3 infected recipients and 1 additional recipient were treated without incident. CONCLUSION Physicians should consider babesiosis in the differential diagnosis of a febrile hemolytic disorder after blood transfusion. Prompt diagnosis is important since babesiosis is responsive to antibiotic therapy and, untreated, can be a fatal disease in certain risk groups.