Naturally Acquired HumanPlasmodium knowlesiInfection, Singapore

We report a case of naturally acquired Plasmodium knowlesi in Singapore, a malaria-free country.Diagnosis was confi rmed by PCR with validated species-specifi c primers.In industrialized countries, free-ranging primates are a potential source of P. knowlesi human infection.P. knowlesi infection is a differential diagnosis of febrile illness acquired in Singapore.P lasmodium knowlesi is one of the simian malarias that causes human infection (1,2).All 6 published reports of naturally acquired P. knowlesi infection were in rural settings with the largest case series being reported from East Malaysia (3-8).P. knowlesi is commonly misidentifi ed as P. malariae since the blood stages are morphologically similar on microscopy, and molecular methods of detection are necessary for accurate diagnosis (5,8).Singapore is an urban city-state, which was declared free of human malaria by the World Health Organization in 1982 (9).However, we report a case of locally acquired P. knowlesi malaria, which indicates that this emerging zoonotic parasite should be considered as an etiologic agent of acute febrile illness acquired in Singapore, the southernmost locale reported thus far.