This illness is a disease caused by a protozoan, carried by ticks, most commonly by the nymphal stage of Ixodes scapularis . Actual incidence is unknown, as there are only 450 cases on record from widely geographically separated regions. Symptoms, if any, generally begin within a week of being bitten by a tick. In people with intact spleens, prognosis for recovery is far better than for those whose spleens have been removed due to previous trauma or illness. Of the latter group, most die.
Treatment begins with at least seven days of medication, either given by mouth or intravenously.
Patients with very severe cases may require a complete exchange transfusion of blood. Symptoms may persist for months.