MMWR: Morbidity and Mortality Weekly Report: Surveillance Summaries, March 4, 2016 [open pdf - 665KB]
"Malaria in humans is caused by intraerythrocytic protozoa of the genus Plasmodium. These parasites are transmitted by the bite of an infective female Anopheles mosquito. The majority of malaria infections in the United States occur among persons who have traveled to regions with ongoing malaria transmission. However, malaria is also occasionally acquired by persons who have not traveled out of the country through exposure to infected blood products, congenital transmission, laboratory exposure, or local mosquitoborne transmission. Malaria surveillance in the United States is conducted to identify episodes of local transmission and to guide prevention recommendations for travelers."
Morbidity and Mortality Weekly Report: http://www.cdc.gov/mmwr/index.html/
MMWR: Morbidity and Mortality Weekly Report (March 4, 2016), v.65 no.02