Multifocal autochthonous transmission of malaria--Florida, 2003.

The majority of malaria cases diagnosed in the United States are imported, usually by persons traveling from areas where malaria is endemic. However, small outbreaks of locally acquired mosquito-borne malaria continue to occur. During July-September 2003, an outbreak of malaria (eight cases of Plasmodium vivax malaria) occurred in Palm Beach County, Florida. During the same period, two patients were evaluated for malaria in neighboring Okeechobee County, approximately 75 miles from the Palm Beach County transmission area. One patient was thought to have acquired infection with the same parasite species (P. vivax), and concerns were raised about a possible link. To determine whether infection was acquired in Okeechobee County and whether a possible link existed to the Palm Beach County outbreak, the Florida Department of Health (FDOH) initiated an investigation. This report describes that investigation, which determined that although initial laboratory results suggested local transmission, subsequent evaluation and testing confirmed the case as imported malaria. These findings underscore the importance of a rapid and thorough investigation of any malaria case suspected to be acquired through local mosquito-borne transmission.