Abstract: Objective To investigate and analyze the mixed infection of malaria in 6 imported cases with different incubation period for evidence to plan prevention and control measures for imported malaria. Methods Information of the 6 imported cases was collected from the case registration and management system of malaria besides clinical case data from primary medical institutions, microscopic examination and recheck findings by PCR performed in provincial reference laboratory. Results All of the 6 malaria cases had a history of living abroad, and the shortest time of living abroad was 10 days and the longest 1 229 days. After returning to China, they never went abroad again. The first onset for the 6 cases ranged from 1 to 10 days after their return, initially diagnosed as Plasmodium falciparum infection, and discharged following antimalarial medication. The interval was 22 ~ 133 days between discharge from hospital and the second attack. Three of the six cases were diagnosed as coinfection with P. falciparum and P. malariae, and another three as coinfection with P. falciparum and P.ovale. The infected plasmodium species in twice attacks in the 6 cases were subjected to microscopic examination and PCR recheck performed in the provincial reference laboratory. All patients were followed for over one year after discharge from the second attack, and well recovered. Conclusion The 6 cases of imported malaria with different incubation period are associated with P. falciparum and P. ovale infection or mixed P. malariae infection. The findings suggest that prevention and control of such cases should be strengthened in the future in order to consolidate efforts in elimination of malaria.

Key words: P. falciparum , P. ovale ,  P. malariae , Mixed infection, Malaria elimination, Jiangsu Province