Risk factors for serious infection with Babesia species:
(1) increasing age
(1a) Children usually do not have serious infections unless there is an underlying condition present. Neonates can be at increased risk.
(1b) Patients > 50 years of age (some say > 40) have greater risk of serious infection than younger patients.
(2) asplenia or splenectomy
(3) immunosuppression, including AIDS or organ transplantation
(4) one or more serious comorbid conditions (cancer, cardiac, lung, liver, etc)
(5) concurrent Lyme disease
(6) hemoglobinopathy associated with splenomegaly
(7) therapy with anticytokine therapy (etanercept, infliximab, etc)