Division of Malaria and Parasitic Diseases, National Institute of Health, Korean Centers for Disease Control and Prevention, Seoul 122-701, Korea.
We report on the first case of human babesiosis in Korea. The intraerythrocytic parasite (KO1) in the patient's blood mainly appeared as paired pyriforms and ring forms; but Maltese cross forms were not seen, and the parasite showed morphological features consistent with those of the genus Babesia sensu stricto. The sequence of the 18S rRNA gene of KO1 was closely related to that of Babesia spp. isolated from sheep in China (similarity, 98%). The present study provides the first evidence of the presence of a hitherto unidentified, new type of Babesia parasite capable of infecting humans.