What is the prognosis of babesiosis?

Updated: Apr 01, 2021
  • Author: Rachel E Strength, MD; Chief Editor: Michael Stuart Bronze, MD  more...
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Babesiosis in otherwise healthy hosts may produce an acute infectious condition that resembles malaria. However, most cases of babesiosis are subclinical or only mildly symptomatic. In the United States, the prognosis for babesiosis is excellent; most patients recover spontaneously. About 25% of adults and 50% of children infected with Babesia are asymptomatic and improve spontaneously without treatment. Fewer than 10% of US patients with babesiosis have died; most of these have been elderly or asplenic.

In patients who are asplenic, babesiosis can be quite severe and is associated with substantial mortality. Asplenic patients tend to have a more fulminant and prolonged clinical course. [23]  Highly immunocompromised patients are at a higher risk for complications such as acute respiratory distress syndrome, shock, warm autoimmune hemolytic anemia, heart failure, and death. [3]  In a 1998 review by White et al, 9 of 139 (6.5%) patients who were hospitalized with babesiosis in New York State from 1982-1983 died. [24]  

Immunocompromised patients are at a higher risk of relapse, especially if they have HIV with acquired immunodeficiency syndrome (AIDS), if they are transplant patients on immunosuppression, if they are receiving rituximab, or if they have malignancy and asplenia. [3]

In Europe, babesiosis often comes from B. divergens, which can cause life-threatening infection. About 83% of infected European patients are asplenic, contributing to a poor prognosis. More than 50% of patients with babesiosis in Europe become comatose and die.

Deaths have been reported from transfusion-transmitted babesiosis within the immunocompromised population in areas where Babesia infection is not endemic. [25]  The mortality rate of B.microti infection from a transfusion is about 20%. [3]

Approximately 10-20% of patients with babesiosis are co-infected with Lyme disease. [3] The symptoms experienced by these patients are more severe and prolonged than symptoms experienced by patients who have either disease alone. Babesia co-infection should be considered when a patient with Lyme disease does not respond to typical therapy or when a patient with Lyme disease has atypical symptoms.

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