Plasmodium falciparum resistant to chloroquine sulfate has now been documented in two nonimmune travelers exposed in Tanzania and Kenya. Symptoms of malaria developed after their return to the United States. Laboratory studies confirming prior ingestion of chloroquine and showing resistance of the parasites to chloroquine in vitro provide key elements of the documentation. This work adds to the data establishing the presence of chloroquine-resistant P falciparum in Africa.
Areas of the world from which chloroquine-resistant P falciparum has been reported now include Kenya, Tanzania, Nigeria, and Ivory Coast in Africa; Brazil, Colombia, Ecuador, French Guiana, Guyana, Panama, Surinam, and Venezuela in the Americas; and Bangladesh, Democratic Kampuchea, India, Indonesia, Laos, Malaysia, Papua New Guinea, the Philippines, Thailand, and Vietnam in Asia. Chloroquine-resistant P falciparum is prevalent throughout malarious areas in some countries such as Thailand; in others it has been documented or reported either sporadically or only in certain parts