Abstract: Objective To find out the infection source of a quartan malaria case. Methods The clinical, laboratory and epidemiological information of the patient was collected. The epidemiological investigation and rapid diagnostic test （RDT） were conducted in the surrounding population. Vectors were investigated. Results Blood film test showed the presense of Plasmodium malariae. Bone marrow aspiration revealed active proliferation of bone marrow as well as granulocytes, red blood cells and giant cells. RDT test showed positive result for Plasmodium. Nested PCR resulted in a specific band of 144 bp, consistent with the positive control. The patient was treated with dihydroartemisinin piperaquine phosphate tablet（2 tab×bid×2 d, po）. Tracing investigation showed that the patient had no history of surgery or blood transfusion within 3 years before the disease onset, and had travelling history in Hainan Province and Haimen City in 2005 and 2013 respectively. There was no case of local infection within 5 years in the patient’s area of residence. Twenty-five families including 35 individuals in the area where the patient lived were investigated and all had negative results for the RDT test. In addition, none showed symptom of fever within the past 2 weeks. No Anopheles sinensis was found in the vector investigation. Conclusion This is a case of quartan malaria with a long latency, and the patient has been infected in other provinces.

Key words: Quartan malaria, Long latency, Tracing investigatition