The CDC
http://www.cdc.gov/malaria/features/surveillance.htm
says there were 10 cases of malaria contracted in the US in 2003, and about twelve hundred cases overall (those not contracted in the US were contracted during overseas travel); seven people died.

I'd guess the major benefit of this drug approval is for people traveling to areas where malaria is a risk. Coartem is used to treat malaria; it does not work as a preventive.