Yun Lu,1,2,* Dan Zhang,2– 4,* Dongsheng Han,2– 4 Fei Yu,2– 4 Xingnong Ye,5 Shufa Zheng2– 4 

1Department of Clinical Laboratory, The Children’s Hospital, Zhejiang University School of Medicine, National Clinical Research Center for Child Health, National Children’s Regional Medical Center, Hangzhou, People’s Republic of China; 2Department of Laboratory Medicine, the First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, People’s Republic of China; 3Key Laboratory of Clinical in vitro Diagnostic Techniques of Zhejiang Province, Hangzhou, People’s Republic of China; 4Institute of Laboratory Medicine, Zhejiang University, Hangzhou, People’s Republic of China; 5Department of Hematology, the First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, People’s Republic of China

*These authors contributed equally to this work

Correspondence: Shufa Zheng, Department of Laboratory Medicine, the First Affiliated Hospital, Zhejiang University School of Medicine, No. 79, Qingchun Road, Hangzhou, 310003, People’s Republic of China, Email zsfzheng@zju.edu.cn Xingnong Ye, Department of Hematology, the First Affiliated Hospital, Zhejiang University School of Medicine, No. 79, Qingchun Road, Hangzhou, 310003, People’s Republic of China, Email xingnong@zju.edu.cn

Abstract: Babesiosis, as a vector-borne infectious disease, remains relatively rare and is prone to being overlooked and misdiagnosed. Therefore, understanding the epidemiological characteristics and clinical manifestations of babesiosis is crucial for the prompt detection and treatment of the disease. We reported a 63-year-old male patient presenting with spontaneous fever and chills. Laboratory investigations revealed erythrocytopenia, reduced hemoglobin levels, and increased reticulocytes and total bilirubin. Bone marrow examination indicated vigorous cell proliferation, a decreased granulocyte to red cell ratio, and predominant erythroid cell proliferation, with a higher prevalence of intermediate and late-stage juvenile granulocyte and erythroid cells. Initial treatment focused on hemophagocytic syndrome triggered by Epstein-Barr virus infection yielded unsatisfactory results, leading to secondary multiple pulmonary infections. Metagenomic next-generation sequencing (mNGS) of sputum samples pointed to hemolytic anemia induced by Babesia infection, which was subsequently confirmed through peripheral blood smear analysis. The patient responded well to prompt administration of atovaquone and azithromycin, with symptoms resolving and laboratory parameters normalizing. Hemolytic anemia resulting from babesiosis should be distinguished from hemophagocytic syndrome caused by Epstein-Barr virus and other hematologic conditions. mNGS represents an efficient technique for Babesia detection.

Keywords: Babesia, Hemolytic anemia, mNGS, Pneumonia