As has been noted previously malaria was a severe scourge in much of the area of the southeastern states of the USA and as far north as southeast Canada. With the disappearance of endemic malaria, the importance of malaria for both countries is primarily as an imported disease. Since 1957, nearly all cases of malaria diagnosed in the USA have been imported. Approximately half the cases of imported malaria occur among USA-born civilians and half among foreign-born civilians, many of whom contract malaria while visiting their countries of origin. Malaria frequently occurs among military service men returning from endemic countries who have not complied with recommended chemoprophylaxis recommendations. In the USA, about 1200–1500 malaria cases are reported annually which are mostly attributed to imported malaria. These cases describe travellers or immigrants coming from malaria-endemic areas, where they were infected, and developing signs of malaria after arriving in the USA.

A total of 1337 cases of malaria, including 8 deaths, were reported for the year 2002 in the USA. Of these 1337 cases, all but 5 were imported, i.e., acquired in malaria-endemic countries. The USA Centers for Disease Control (CDC) report that in the USA, between 1957 and 2003, 63 outbreaks of locally transmitted mosquito-borne malaria have occurred; in such outbreaks, local mosquitoes become infected by biting persons carrying malaria parasites (acquired in endemic areas) and then transmit malaria to local residents.