Increasing number of imported Plasmodium ovale wallikeri malaria in Shandong Province, China, 2015-2017.

Since 2012, no indigenous malaria case have been reported in Shandong Province, China, whereas the number of imported cases and the genetic diversity of Plasmodium spp. have increased. Beginning in 2015, the number of Plasmodium ovale cases were increased and the P. ovale wallikeri malaria case began to arise. From 2015 to 2017, a total of 676 imported malaria cases were detected and 76 P. ovale spp. isolates were identified, of which 48 were P. ovale curtisi and 28 P. ovale wallikeri. The number of P. ovale wallikeri malaria cases increased yearly, six were identified in 2015, eight were identified in 2016, and 14 were identified in 2017. All cases with an attached travel history from Africa, with represented source countries of Equatorial Guinea (n = 9), Republic of the Congo (n = 4), and Democratic Republic of the Congo (n = 3). P. ovale wallikeri is increasing among travelers returning to Shandong Province from Africa. Although the P. ovale spp. infection rarely progressed to severity, this species is suspected to generate hypnozoites which have the potential to relapse. The ability to cause relapse is the threat to public health and should be concerned.