Until the mid-1970s, most cases of imported malaria in the United States occurred in war veterans who had acquired the disease while on overseas duty.
Outbreaks of nonimported (indigenous) cases of malaria, which appear to be associated with infected migrant workers, have occurred in southern California (mostly in San Diego County) and Florida (Branati et al., 1954; Centers for Disease Control, 1991f). These outbreaks have been small and so far relatively isolated, but the potential exists for the disease to become reestablished in the United States, since competent mosquito vectors are present in abundance. In fact, secondary cases in local contacts of individuals with imported disease are periodically recognized (Maldonado et al., 1990; Centers for Disease Control, 1991f).
In the areas of California and Florida where malaria outbreaks have occurred, sanitary facilities and housing are often substandard, a fact that can complicate vector-control efforts as well as medical treatment. Finding and treating illegal migrant workers infected with the malaria parasite are especially hard. The demand for cheap migrant labor and the limited availability of housing and health care for these workers may mean that the